ICSE CHAPTERWISE PYQ CLASS 10 BIOLOGY PAGE 5

CHAPTER 1
CELL CYCLE AND STRUCTURE OF CHROMOSOMES

1. CELL DIVISION 4. MITOTIC PHASE OR MITOSIS (DIVIDING PHASE)

Cell Division is a method by which new cells are It is the dividing phase during which nucleus as
originated from pre-existing cells. These new cells well as cytoplasm divide into two daughter cells.
need to be produced for growth, development, It is studied in two parts :
replacement, repair and reproduction. All (i) Karyokinesis (ii) Cytokinesis
organisms contain an even number (2n) of (i) Karyokinesis (Division of nucleus) : In this
chromosomes in their somatic or body cells. The many events take place in a sequence which
cell division leading to growth, development, are studied in four stages.
repair and replacement is called Mitosis. The cell 1. Prophase : It begins with the appearance
division leading to production of gametes (sex of chromosomes which have become
cells) is called meiosis. short, thick and clearly visible inside the
nucleus. Each chromosomes get duplicated
2. CELL CYCLE by splitting longitudinally to form two
The sequence of events including growth and chromatids which are attached to each
division, that a cell undergoes from the time of other at a small region called centromere.
its formation upto its division into daughter cells The centrosome (in animal cell) splits into
is called cell cycle. Every cell capable of division two along with duplication of centrioles
passes through cell cycle which consists of two which move towards opposite poles of
phases : the cell. Each centriole is surrounded
1. Interphase [Resting or non-dividing phase; I by asters (centrioles along with astral
phase] rays). A number of spindle fibres appear
2. Mitotic phase or Mitosis [Dividing phase; M between two daughter centrioles.
phase] In plant cell due to the absence of
centrosome (centriole), the formation of
3. INTERPHASE (RESTING PHASE) spindle fibres take place from cytoplasmic
It is the non-dividing preparatory phase during strands (microtubules) of the cell.
which a cell grows to its maximum size (by The nuclear membrane and nucleolus
increase in volume of nucleus and nucleolus) and disappear. The chromosomes start
the synthesis of DNA (chromosome material) moving towards equator of the cell.
takes place. Due to the duplication of DNA 2. Metaphase : The chromosomes get
contents the chromatin material also duplicates . arranged at the equatorial plate of the
Interphase is divided into three sub-stages. cell. Each chromosomes get attached
(a) G1 – phase : Volume of cytoplasm increases itself to a spindle fibre by its centromere.
and protein synthesis takes place. 3. Anaphase : Centromere divides and two
(b) S – phase : Synthesis of DNA takes place. sister chromatids of each chromosome
(c) G2 – phase : Necessary spindle proteins are separate and are drawn apart towards
synthesized. opposite poles to form two groups of
The cell is quite active metabolically during chromosomes.
this phase and several processes, including DNA 4. Telophase : Each Chromatid or daughter
synthesis, occur at this time, thus no alternative chromosome turns into a network of
is left for the cell except to divide by the process chromatin threads. Nuclear membrane
of mitosis. and nucleolus reappear.
(ii) Cytokinesis (Division of cytoplasm) : A
constriction (furrow) appears in the cell
CH 1 : CELL CYCLE AND STRUCTURE OF CHROMOSOMES

membrane at the middle of the animal cell,

which deepens and finally splits the cytoplasm
into two, thus producing two new cells. In
plant cell instead of a furrow, a cell plate is
laid down in the cytoplasm at the equatorial
plate. It grows from centre to periphery, thus
dividing the original cell into two daughter
cells.
Note : In Mitosis, two identical daughter
cells are produced by division of one parent
cell. The main aspect of this division is that
the same normal chromosome number is
maintained at each division of the cell. Hence,
it is also called as Equational cell division.
Identification points of Mitosis :
1. Prophase – Chromosomes with two
chromatids, disappearance of nuclear
membrane as well as nucleolus and formation
of the spindle.
2. Metaphase – Chromosomes arranged at
equatorial plate.
3. Anaphase – Movement of daughter
chromosomes towards pole.
4. Telophase – Uncoiling of chromosomes,
disappearance of spindle, reappearance of 4.1 Significance of Mitosis
nucleolus and nuclear membrane.
The Significance of Mitosis are as follows :
Differences between mitosis in animal and plant
1. Helps in growth of animals and plants.
cell are as follows :
2. It replaces old and dead cells.
Animal cell Plant cell 3. Repairs damaged and wounded tissues of
animals and plants.
1. Spindle formed is 1. Spindle formed is
4. Helps in asexual reproduction in unicellular
amphiastral. anastral.
organisms.
2. Cytokinesis by 2. Cytokinesis by 5. Maintains same number of chromosomes in
constriction formation of cell daughter cells.
(furrow) method. plate.
5. MEIOSIS
3. Cytokinesis 3. Cytokinesis
It is the kind of cell division that produces sex
proceeds from proceeds from
cells or gametes. It takes place in the reproductive
outside to centre. centre towards
organs, i.e., testis to produce sperms and ovary
periphery.
to produce egg or ovum in humans. In Plants, it
4. Centrosome 4. Centrosome takes place in anthers to produce pollen grains
present so 2 absent so no and ovules in ovary to produce egg or oosphere.
asters are formed. asters are formed. The number of chromosomes in this type of cell
division is reduced to half in the daughter cells.
Meiosis consists of two separate divisions of sex
cells:
(i) Meiosis I (Heterotypic or reductional division)
: This division is meiotic in which the
chromosome number is reduced to half (n).
(ii) Meiosis II (Homotypic or equational division)
: This division is mitotic. Each of the two
cells formed in meiosis I further divides
ICSE CHAPTERWISE PYQ CLASS 10 BIOLOGY PAGE 7

into two, resulting in the formation of four The chromosomes consist of about 40% DNA
daughter cells, each with haploid (n) number and about 60% histones (a particular type of
of chromosomes. protein). The histones and DNA form a kind of
complex in which the DNA strands wind around
5.1 Significance of Meiosis histone molecules. Each such complex is called
Significance of Mitosis are as follows : nucleosomes. A single human chromosome may
1. In sex cells (gametes), chromosome number have about a million nucleosomes.
is halved so that on fertilization the normal The DNA is a very large single molecule
number (2n) is restored. (macromolecule) which is composed of two
2. Helps in mixing up of genes which increases strands, wound around each other in a double
the genetic vigour. helix manner.
3. Helps in causing variations which further
leads to evolution. 6.1 Nucleic Acid
Differences between Mitosis and Meiosis are as Chemical analysis of chromosomes show two nucleic
follows : acids DNA and RNA. They were first discovered
by Frederick Miesher. Nucleic acids have complex
Mitosis Meiosis chemical structures composed of pentose sugars,
1. Occurs in somatic Occurs in nitrogenous bases and phosphates. The DNA and
cells of haploid reproductive cells of RNA differ from each other as follows :
as well as diploid diploid organisms
organisms. only. DNA RNA

2. It produces two It produces four 1. Found in nucleus, Found in cytoplasm,

daughter cells. daughter cells. mitochondria and nucleolus and
chloroplast. chromosomes.
3. It is completed in It is completed
one division. in two successive 2. Pentose sugar is Pentose sugar is
divisions. deoxyribose. ribose.

4. It is equational It is reductional 3. Mostly double Mostly single

division. division. stranded. stranded.

5. Genetic constitution Genetic constitution 4. Concerned with Concerned with

of daughter cells of daughter cells genetic information. synthesis of
remains the same. becomes different. proteins.

6. No synapsis takes Synapsis occurs

6.2 Genes
place. during prophase I.
The specific parts of chromosomes, which are
7. No crossing over Crossing over takes
composed of DNA are called Genes. They
takes place. place in prophase I.
determine hereditary characters. They are
8. It takes place It takes place responsible for transmission of characters from
during growth, during reproduction one generation to another. They are located in
repair, regeneration of an organism. the chromosomes and occupy a fixed position in
and development of the chromosome. Scientists have identified around
an organism. 1,30,000 genes in human chromosomes.
Every human body cell has the same number
6. CHROMOSOMES of chromosomes and possesses nearly all normal
These are small but thick, rod like darkly stainable genes. Some of the genes are active in all the
structures seen in the nuclei of dividing cells only cells such as genes for cell respiration, as every
at metaphase and anaphase stage of cell division. cell needs to respire. Some genes though present
Hofmeister discovered chromosomes for the first in all the cells are active only in the particular
time. Each chromosome in its condensed form specialized body cells such as, genes for producing
consists of two chromatids joined at one point insulin is present in every cell but functionally it
called centromere and the parts of chromatids on expresses only in beta cells of islets of langerhans
the two sides of a centromere are called arms. of pancreas.
CH 1 : CELL CYCLE AND STRUCTURE OF CHROMOSOMES

6.3 Types of Chromosomes

MULTIPLE CHOICE QUESTION
Chromosomes are divided in the following parts :
1. Metacentric : Centromere in the centre and
two arms of chromatid are equal. 1. Duplicated chromosomes are joined at a point
2. Submetacentric : Centromere slightly away termed:
from centre and one arm of chromatid is (a) Centrosome (b) Centromere
slightly larger than other. (c) Centriole (d) Chromatid
3. Acrocentric Centromere is present near one Ans : MAIN 2024
end of chromatid and one arm is very large
than the other. Duplicated chromosomes consist of two identical
4. Telocentric : Centromere is present at one end sister chromatids joined together at a point called
of chromosome. the centromere.
Thus (b) is correct option.

2. A female human cell divides through mitosis,

maintaining the same number of chromosomes.
Consider the chromosome composition of the
daughter cells after mitosis. After Mitosis, a
female human cell will have :
(a) 44 + XX chromosomes.
(b) 22 + X chromosomes.
(c) 22 + Y chromosomes.
7. TELOMERE (d) 44 + XY chromosomes.
Telomere is terminal end of chromosome that Ans : COMP 2021
consists of many copies of a repeated DNA If a female cell with 44+XX chromosomes divides
sequence. mitotically, it will form 2 daughter cells with
The chromosomes which determine the sex of an similar chromosomes i.e. 44+XX whereas a male
individual are called allosomes or idiosomes or sex cell will mitotically divide to form cells with
chromosomes. The 23rd pair of human chromosomes chromosome 44+XY
(X and Y) are called as sex chromosomes. Thus (a) is correct option.
1 – 22 pairs of human chromosomes are called as
autosomes. 3. At the end of______Cytokinesis is completed.
The chromosome number of some common animals (a) Metaphase (b) Prophase
and plants organisms in pairs are as follow : (c) Interphase (d) Telophase

1. Ascaris = 1 pair Ans : SQP 2021

2. Frog = 13 pairs Cytokinesis begins in anaphase and ends in

telophase, reaching completion as the next
3. Humans = 23 pairs interphase begins.
4. Gorilla = 24 pairs Thus (d) is correct option.
5. Rabbit = 22 pairs 4. The nitrogenous base Adenine always pairs
6. Rat = 21 pairs with______.
7. Lion, tiger and cat = 19 pairs (a) Thymine (b) Guanine
(c) Cytosine (d) Thiamine
8. Dog and fowl = 39 pairs
Ans : MAIN 2021
9. Onion = 8 pairs
Adenine pairs with Thymine in DNA through
10. Maize = 10 pairs two hydrogen bonds, maintaining the double-
11. Potato = 24 pairs helix structure. This pairing follows specific base-
12. Garden Pea = 7 pairs pairing rules, ensuring accurate DNA replication.
The Adenine-Thymine pairing complements the
Guanine-Cytosine pairing.
Thus (a) is correct option.
ICSE CHAPTERWISE PYQ CLASS 10 BIOLOGY PAGE 9

5. Replication of DNA in the cell cycle occurs during distribution of chromosomes is:
the : (a) Splitting of the centromeres
(a) G1 - phase (b) Anaphase (b) Splitting of the chromatids
(c) S - phase (d) G2 - phase (c) Replication of the genetic material
(d) Condensation of the chromatin
Ans : MAIN 2021

S-phase is the period during which DNA Ans : MAIN 2017

replication occurs. Anaphase is marked by splitting of centromere

Thus (c) is correct option. and contraction of spindle fibers which in turn
move the sister chromatids towards the opposite
6. State the functions of Centromere : poles.
(a) It is the point of attachment of two sister Thus (a) is correct option.
chromatids.
(b) It is the point of attachment of two centrioles. 10. Which of the following descriptions of mitosis is/
(c) It is the point of attachment of two are correct?
centrosomes. (i) DNA synthesis occurs at the beginning of
(d) It is the point of attachment between two prophase.
daughter nuclei. (ii) The nuclear envelope breaks down in prophase
and reforms in telophase.
Ans : COMP 2021
(iii) The division of centromeres occurs in
The centromere is a region on a chromosome that anaphase.
links two sister chromatids. During cell division, (a) 1, 2 and 3 (b) Only 1 and 2
it also serves as the attachment point for spindle (c) Only 2 and 3 (d) Only 1
fibers, ensuring proper segregation of chromatids
to daughter cells. Ans : SQP 2010

Thus (a) is correct option. Mitosis is a cell division in which a single cell
divides into two identical daughter cells. In
7. The cell component visible only during cell prophase, the nuclear envelope breaks down and
division ______ reforms in telophase. The division of centromeres
(a) Mitochondria (b) Chloroplast occurs in anaphase.
(c) Chromosome (d) Chromatin Thus (c) is correct option.
Ans : SQP 2013
11. The stage in which daughter chromosomes move
The genetic material, i.e. DNA, is present as toward the poles of the spindle is:
chromatin fibres in a non-dividing cell. Only during (a) Anaphase (b) MetaPhase
particular stages of cell division are chromosomes (c) Prophase (d) TeloPhase
visible. The coiling and supercoiling of chromatin
fibres forms chromosomes. Because chromosomes Ans : COMP 2022

are substantially condensed during cell division, In anaphase, the centromere splits and
they can be seen under a light microscope. chromosomes move apart towards two opposite
Thus (c) is correct option. poles due to shortening of spindle fibers.
Thus (a) is correct option.
8. Chromosomes get aligned at the centre of the cell
during : 12. During cell division, a specific cell component
(a) Metaphase (b) Anaphase becomes distinctly visible, aiding in the
(c) Prophase (d) Telophase. distribution of genetic material. This component
is otherwise not clearly seen in non-dividing
Ans : SQP 2015
cells. The cell component visible only during cell
Attachment of chromatids to the mitotic spindle division.
and chromatid alignment on the equatorial plate (a) Mitochondria (b) Chloroplast
are both part of metaphase. (c) Chromosome (d) Chromatin
Thus (a) is correct option.
Ans : MAIN 2019
9. The major event that occurs during the anaphase The cell component visible only during cell
of mitosis, which brings about the equal division is the chromosome. The highly condensed
CH 1 : CELL CYCLE AND STRUCTURE OF CHROMOSOMES

and coiled chromatin fibers which appear during Ans : MAIN 2002

karyokinesis are called chromosomes. Mitosis is used to produce daughter cells that
Thus (c) is correct option. are genetically identical to the parent cells. The
cell copies – or ‘replicates’ - its chromosomes (as
13. Which of the events listed below is not observed well as the genes), and then splits the copied
during mitosis? chromosomes equally to make sure that each
(a) Chromatin condensation daughter cell has a full set.
(b) Movement of centrioles to opposite poles Thus (b) is correct option.
(c) Appearance of chromosomes with two
chromatids joined together at the centromere. 17. Spindle fibres play an important role in mitosis
(d) Crossing over and meiosis. Which biological molecule are spindle
Ans : SQP 2005
fibres composed of?
(a) Polysaccharide (b) Protein
Crossing over occurs during prophase I of meiosis. (c) nucleic acid (d) Lipid
Thus (d) is correct option.
Ans : SQP 2000
14. Which kind of cell division taking place in each of Spindle fibers also known as mitotic spindle are
the following options is incorrect? the cellular structures which are mainly used
(a) At the tip of the root : Mitosis during cell division. It forms a protein structure
(b) To produce pollen grains : Meiosis which helps in cell division. It is made up of
(c) To add girth to the stem : Mitosis tubulin protein.
(d) To produce egg: Mitosis Thus (b) is correct option.
Ans : COMP 2009
18. Two daughter cells formed during mitosis contain
Female gametes are called ova or egg cells and (a) the same amount of DNA,S but a set of
male gametes are called sperm. These reproductive chromosomes different from those of the
cells are produced through a type of cell division parent cell.
known as meiosis. (b) the same amount of DNA and the same set of
Thus (d) is correct option. chromosomes as those of the parent cell.
(c) half the amount of DNA and the same set of
15. Which of the following options are the pyrimidine
chromosomes as those of the parent cell.
bases found in DNA?
(d) double the amount of DNA and a set of
(a) Uracil and Thymine
chromosomes different from those of the
(b) Thymine and Cytosine
parent cell.
(c) Adenine and Thymine
(d) Cytosine and Uracil Ans : SQP 2008

Ans : SQP 2020 Thus (b) is correct option.

The pyrimidine bases present in the DNA are 19. Abnormal and uncontrolled mitosis in an organ
cytosine and thymine. Apart from the pyrimidine will result in:
bases, purine bases are also present — adenine (a) gamete (b) Zygote
and guanine. (c) Cancer (d) None of these
Thus (b) is correct option.
Ans : MAIN 2010
16. Chromosomes and genes both play a crucial Cancer is a group of diseases characterized by
role in inheritance and cellular function. During uncontrolled cell division —mitosis.
cell division, they ensure the transfer of genetic Thus (c) is correct option.
information to daughter cells, maintaining
consistency across generations Which statement 20. Meiotic division occurs in
is true of both chromosomes and genes? (a) vegetative cells
(a) Each codes for a specific protein. (b) reproductive cells
(b) Each may be copied and passed on in mitosis. (c) meristematic cells
(c) Each may be either dominant or recessive. (d) none of these.
(d) Each may exist as two or more alleles.
Ans : SQP 2016
ICSE CHAPTERWISE PYQ CLASS 10 BIOLOGY PAGE 11

The meiotic division takes place in the reproductive Ans : SQP 2017

cells. Metaphase is the best time to count and study

Thus (b) is correct option. the number and morphology of chromosomes.
Thus (d) is correct option.
21. Identify the wrong statement about meiosis:
(a) Pairing of homologous chromosomes. 25. Which of the following bonds are broken during
(b) Four haploid cells are formed. DNA replication?
(c) At the end of meiosis the number of (a) Hydrogen bonds between bases.
chromosomes are reduced to half. (b) Phosphodiester bonds.
(d) Two cycle of DNA replication occurs. (c) Covalent bonds between bases.
Ans : MAIN 2003
(d) Ionic bonds between bases and phosphate
groups.
S phase (Synthesis Phase) is the phase of the
cell cycle in which DNA is replicated, occurring Ans : MAIN 2022

between G1 phase and G2 phase. During DNA replication, the hydrogen bonds
Thus (d) is correct option. must be broken between the complementary
nitrogenous bases in the DNA double helix. Once
22. What defines a diploid nucleus? this is accomplished, either side of the DNA
(a) A nucleus containing two unpaired molecule can act as a template to produce another
chromosomes. double stranded DNA molecule.
(b) A nucleus with two alternative forms of a Thus (a) is correct option.
gene.
(c) A nucleus with two separate threads of DNA. 26. Which of the following is incorrect regarding
(d) Anucleus containing two sets of chromosomes. structure of DNA?
Ans : SQP 2008
(i) Nucleotide is composed of pentose sugar,
nitrogenous bases and phosphate group.
A diploid nucleus describes a cell, nucleus, or (ii) Adenine pairs with Thymine and Guanine
organism containing two sets of chromosomes pairs with Cytosine.
(2n). (iii) A = T, C = G
Thus (d) is correct option. (iv) DNA strand winds around the nucleosome,
which consists of eight pairs of histone
23. When a cell divides, these events occur. proteins.
(i) The DNA inside the cell is duplicated exactly. (v) Genes are the fundamental unit of DNA.
(ii) Daughter cells are produced with the same (a) (ii) and (iii) only (b) (i), (ii), (v) only
chromosome number as the parent cell. (c) (iii) and (iv) only (d) None of them
Which type of division has occurred?
(a) Meiosis producing genetically different cells. Ans : COMP 2020

(b) Meiosis producing genetically identical cells. The bases on the opposite strands are connected
(c) Mitosis producing genetically different cells. through hydrogen bonds forming base pairs
(d) Mitosis producing genetically identical cells. (bp). Adenine always forms two hydrogen bonds
Ans : COMP 2001 with thymine from the opposite strand and vice-
versa. Guanine forms three hydrogen bonds with
During mitosis, the following events takes place: cytosine from the opposite strand and vice-versa.
(i) The DNA inside the cell is duplicated exactly. A nucleosome is a section of DNA that is wrapped
(ii) Daughter cells are produced with the same around a core of proteins. Thus, option (iii) and
chromosome number as the parent cell. (iv) are incorrect.
Thus (d) is correct option. Thus (c) is correct option.

24. If you are provided with root-tips of onion in your 27. How does a haploid nucleus differ from a diploid
class and are asked to count the chromosomes nucleus of the same species?
which of the following stages can you most (a) It has different genes.
conveniently look into: (b) It has fewer chromosomes.
(a) Prophase (b) Anaphase (c) It has more alleles.
(c) Telophase (d) Metaphase (d) It is the result of fertilisation.
CH 1 : CELL CYCLE AND STRUCTURE OF CHROMOSOMES
Ans : MAIN 2023
31. The two chromatids of a metaphase chromosome
The haploid nucleus has half the chromosomes represent:
present in a diploid nucleus. (a) Homologous chromosome of a diploid set.
Thus (b) is correct option. (b) Replicated chromosomes to be separated at
anaphase.
28. Which of these structures, involved in cell (c) Non-homologous chromosomes joined at the
division, is present in animal cells but not higher centromere.
plant cells? (d) Matemal and paternal chromosomes joined at
(a) Centriole the centromere.
(b) Centromere
(c) Chromatid Ans : COMP 2013

(d) Chromosome A chromosome consists of two sister chromatids

joined at the centromere. In the anaphase stage,
Ans : SQP 2018
the centromere splits and the two sister chromatids
Paired organelles called centrioles, typically found move to opposite poles.
together near the nucleus in the centrosome, exist Thus (b) is correct option.
primarily in animal cells and serve to control
spindle fibre formation and which later has an 32. Select the correct statement about G 1 phase:
effect on chromosome separation. Centrioles are (a) Cell is metabolically inactive.
absent from the cells of higher plants. (b) DNA in the cell does not replicate.
Thus (a) is correct option. (c) It is not a phase of synthesis of macromolecules.
(d) Cell stops growing.
29. Chromosomes get aligned at the centre of the cell
during : Ans : MAIN 2007

(a) Metaphase The G1 phase is the first of four phases of the cell
(b) Anaphase cycle that takes place in eukaryotic cell division.
(c) Prophase In this part of interphase, the cell synthesizes m
(d) Telophase RNA and proteins in preparation for subsequent
steps leading to mitosis. DNA in the cell replicates
Ans : MAIN 2014
in the S-phase.
During metaphase, the cell's chromosomes align Thus (b) is correct option.
themselves in the middle of the cell through a
type of cellular "tug of war." The chromosomes, 33. Cytokinesis is the division of
which have been replicated and remain joined at (a) nucleus (b) cytoplasm
a central point called the centromere, are called (c) nucleoplasm (d) none of these.
sister chromatids. Ans : SQP 2016
Thus (a) is correct option.
Cytokinesis is the physical process of cell division,
30. What is produced when a cell undergoes mitosis which divides the cytoplasm of a parental cell into
once? two daughter cells. It occurs concurrently with
(a) Four new cells which are different from each two types of nuclear division called mitosis and
other and from their parent cell. meiosis, which occur in animal cells.
(b) Four new cells which are identical to each Thus (b) is correct option.
other and to their parent cell.
(c) Two new cells which are different from each 34. Cell division by meiosis of a parent cell with 23
other and from their parent cell. pairs of chromosomes will result in:
(d) Two new cells which are identical to each (a) 2 cells, each with 23 pairs of chromosomes.
other and to their parent cell. (b) 2 cells, each with 23 single chromosomes.
(c) 4 cells, each with 23 pairs of chromosomes.
Ans : SQP 2018
(d) 4 cells, each with 23 single chromosomes.
A cell undergoes mitosis to produce two (daughter) Ans : COMP 2023
cells that are genetically identical to the original
(parent) cell. In meiosis the parent cell divides twice to form
Thus (d) is correct option. four cells, each with a single set of chromosomes
(haploid).
ICSE CHAPTERWISE PYQ CLASS 10 BIOLOGY PAGE 13

This means the chromosome number will be daughter cells, each containing the same number
halved to 23 single chromosomes. and kind of chromosomes as the mother cell.
Thus (d) is correct option. Thus (d) is correct option.

35. How many mitotic divisions of a meristematic cell 39. Which of the following might you find in the
in a root tip are needed to produce 256 daughter backbone of DNA?
cells? 1. Phosphate group
(a) 8 (b) 16 2. Hexose sugar
(c) 32 (d) 64 3. Adenine
(a) 1, 2 and 3 (b) 1 only
Ans : SQP 2002
(c) 2 only (d) 1 and 2
Every mitotic division will lead to the formation
of twice the number of mother cells, hence to form Ans : SQP 2002

256 cells from a root tip cell, 8 generations of The backbone of a DNA molecule consists of the
mitotic divisions must occur (28 = 256 cells). phosphate groups and the deoxyribose sugars,
Thus (a) is correct option. whereas the base region of the DNA molecule
consists of the nitrogenous bases; therefore, the
36. Equatorial plane is formed in: backbone of DNA is made up of phosphate groups
(a) Anaphase (b) Metaphase and pentose sugars. Adenine is part of the base
(c) Telophase (d) Interphase region of the molecule. DNA does not contain any
Ans : COMP 2009 hexose (six-carbon) sugars.
Thus (b) is correct option.
During metaphase, all the chromosomes are
aligned on a plane called the metaphase plate, 40. At which stage in mitosis and meiosis do
or the equatorial plane, midway between the two chromosomes always line up at the equator of the
poles of the cell. spindle?
Thus (b) is correct option. (a) Prophase (b) Telophase
(c) Anaphase (d) Metaphase
37. During Telophase, the
(a) nuclear membrane is formed Ans : SQP 2014
(b) nucleolus appears During metaphase, spindle fibers attach to the
(c) astral rays disappear centromere of each pair of sister chromatids. The
(d) all of these sister chromatids line up at the equator, or center,
Ans : SQP 2001 of the cell.
Thus (d) is correct option.
During telophase, a nuclear membrane forms
around each set of chromosomes to separate 41. Which statement describes human cells formed by
the nuclear DNA from the cytoplasm. The meiosis?
chromosomes begin to uncoil, which makes them (a) They are genetically identical and they
diffuse and less compact. become gametes.
Thus (d) is correct option. (b) They are genetically identical and they
become tissues.
38. The following features are shown by the dividing
(c) They are not genetically identical and they
cell in a stage of mitosis: the nuclear membrane
become gametes.
reappears; spindle fibres disappear; chromatids
(d) They are not genetically identical and they
become thin; daughter nuclei are formed. Which
become tissues.
stage is being discussed here?
(a) Prophase (b) Metaphase Ans : MAIN 2012
(c) Anaphase (d) Telophase In meiosis, the parent cell divides twice to form
Ans : MAIN 2010 four cells, each with a single set of chromosomes
(haploid).The gametes produced by meiosis are
During telophase, the chromosomes begin to
not identical because recombination of alleles
decondense, the spindle breaks down, and the
(genes) present on two homologous chromosomes
nuclear membranes and nucleoli re-form. The
occurs during meiosis.
cytoplasm of the mother cell divides to form two
Thus (c) is correct option.
CH 1 : CELL CYCLE AND STRUCTURE OF CHROMOSOMES

42. Which of the following cellular structures always or gametes. Meiosis create genetic variation by
disappears during mitosis and meiosis? making new combinations of gene variants.
(a) Plasma membrane Thus (c) is correct option.
(b) Nucleolus and nuclear envelope
(c) Plastids 46. Duplicated chromosomes are joined at a point
(d) None of these termed:
(a) Centrosome (b) Centromere
Ans : SQP 2015
(c) Centriole (d) Chromatid
The cellular structure that disappears during Ans : COMP 2013
mitosis is nuclear membrane and nucleolus. The
cell then divides by cytokinesis to produce two The centromere is the region where two sister
genetically identical daughter cells. So, the correct chromatids are connected in a duplicated
answer is ‘Nuclear membrane and nucleolus’. chromosome, ensuring correct attachment to
spindle fibers during cell division.
Thus (b) is correct option.
Thus (b) is correct option.
43. A cell has five pairs of chromosomes. After
47. What is not a function of meiosis?
mitotic division, the number of chromosomes in
(a) Producing genetically different cells
the daughter cells will be:
(b) Producing nuclei in ovules
(a) Five (b) Ten
(c) Producing sperm cells
(c) Twenty (d) Forty
(d) Repairing damaged tissues
Ans : SQP 2006
Ans : COMP 2002
The movement of chromatids is carried out by
Repairing damaged tissues is the function of
spindle fibers. If the cell has 5 chromosomes,
mitosis.
during the S-phase it replicates. So, the number
Thus (d) is correct option.
of chromosomes entering mitosis will be 10
chromosomes. During anaphase chromosomes 48. A complex consisting of DNA strand and a core of
split into chromatids. histones is ______
Thus (b) is correct option. (a) Nucleotide (b) Nucleosome
(c) Centrosome (d) Chromosome
44. Which phase comes between G1 and G2 phase?
Ans : COMP 2005
(a) G o phase (b) M - phase
(c) S- phase (d) Interphase Nucleosome is a complex structure in which DNA
wraps around a protein core of eight histone
Ans : MAIN 2021
molecules.
The interphase of the cell cycle comprises G1, Thus (b) is correct option.
S and G2 phase. The S-phase separates the two
growth phases. 49. Meiosis ______ the parental chromosome
Thus (c) is correct option. number.
(a) Doubles (b) Reduces
45. Some features of cell division are listed. (c) Maintains (d) Stabilises
(i) Haploid cells are produced
(ii) New cells are genetically identical Ans : SQP 2000

(iii) Reduction division Meiosis is a type of cell division that reduces the
(iv) Results in variation number of chromosomes in the parent cell by half
Which features would be associated with meiosis? and produces four gamete cells.
(a) (i), (ii) and (iii) (b) (i), (ii) and (iv) Thus (b) is correct option.
(c) (i), (iii) and (iv) (d) (ii), (iii) and (iv)
50. ______ occupies the longest “period in a cell
Ans : SQP 2018
cycle.
During meiosis a diploid cell divides twice to form (a) Interphase (b) Prophase
four daughter cells. These four daughter cells have (c) Metaphase (d) Telophase
half the number of chromosomes of the parent
Ans : MAIN 2009
cell they are haploid. Meiosis produces sex cells
ICSE CHAPTERWISE PYQ CLASS 10 BIOLOGY PAGE 15

During interphase, the cell undergoes normal (a) (i) - (B), (ii) - (C), (iii) - (D), (iv) - (A)
growth processes while also preparing for cell (b) (i) - (D), (ii) - (A), (iii) - (B), (iv) - (C)
division. It is the longest phase of the cell cycle, (c) (i) - (B), (ii) - (A), (iii) - (D), (iv) - (C)
cell spends approximately 90% of its time in this (d) (i) - (D), (ii) - (A), (iii) - (C), (iv) - (B)
phase.
Ans : SQP 2014
Thus (a) is correct option.
In metaphase, chromosomes get arranged in
51. Synthesis phase in the cell cycle is called so, a horizontal plane at the equator. Daughter
because of the synthesis of more ______ chromosomes move to the opposite poles of a
(a) RNA (b) RNA and Proteins spindle in anaphase.
(c) DNA (d) Glucose Chromosomes become visible as fine long
Ans : COMP 2011
threads in prophase Chromosomes lose their
distinctiveness and gradually become transformed
Before the start of karyokinesis, DNA duplication into a chromatin network in telophase.
or semi-conservative replication occurs during the Thus (b) is correct option.
synthesis phase of interphase.
Thus (c) is correct option. 54. Chrosomes get aligned at the centre of the cell
during ______
52. The cell component visible only during cell (a) Metaphase (b) Anaphase
division: (c) Prophase (d) Telophase
(a) Chromosome (b) Chromoplast
Ans : COMP 2022
(c) hromatin (d) Centriole
During metaphase, each chromosome gets
Ans : MAIN 2018
attached to the spindle by its centromere.
The cell component visible only during cell division The chromosomes line up in the centre at the
is chromosome. In a non-dividing cell, DNA is equatorial plane.
present as chromatin fibres. Chromosomes are Thus (a) is correct option.
formed by coiling and supercoiling of chromatin
fibres. Since, during cell division, chromosomes 55. The type of cell division that leads to the formation
are highly condensed, they are visible under light of two identical daughter cells is ______
microscope. (a) Mitosis
Thus (a) is correct option. (b) Genetic recombination
(c) Meiosis
53. Match the events given in Column A with the (d) Cytokinesis
phase in mitotic cell division in Column B and
Ans : SQP 2021
select the correct option.
Mitosis is a process of nuclear division in
Column A Column B eukaryotic cells that occurs when a parent cell
(i) Chromosomes (A) Anaphase divides to produce two identical daughter cells.
get arranged in a Thus (a) is correct option.
horizontal plane at the
56. G1, S and G2 are phases present in______.
equator.
(a) prophase (b) interphase
(ii) Daughter chromosomes (B) Prophase
(c) metaphase (d) anaphase.
move to the opposite
poles of a spindle. Ans : MAIN 2001

(iii) Chromosomes become (C) Telophase A typical cell cycle comprises of interphase
visible as fine long and mitosis. Interphase comprises of G1 or first
threads growth phase, Synthesis or S phase and second
growth phase or G2 phase. G1 phase starts after
(iv) Chromosomes lose (D) Metaphase
cytokinesis, S phase starts after G1 phase and is
their distinctiveness
followed by second growth phase or G2 phase.
and gradually become
Thus (b) is correct option.
transformed into a
chromatin network
CH 1 : CELL CYCLE AND STRUCTURE OF CHROMOSOMES

DIRECTION : Complete the following statements 61. The exchange of chromatid parts between the
with appropriate option . maternal and the patemal chromatids of a pair
of a homologous chromosomes during meiosis is
57. DNA content doubles during ______ ______
(a) Interphase (b) Prophase (a) Crossing over
(c) Metaphase (d) Growth phase (b) Karyokinesis
(c) Meiosis
Ans : COMP 2012
(d) Cytokinesis
During a mitotic cell cycle, the DNA content
Ans : MAIN 2002
per chromosome doubles during S phase (each
chromosome starts as one chromatid, then Crossing over or recombination is the exchange
becomes a pair of identical sister chromatids of chromosome segments between non-sister
during S phase), but the chromosome number chromatids in meiosis. Crossing over creates new
stays the same. combinations of genes in the gametes that are not
Thus (a) is correct option. found in either parent, contributing to genetic
diversity.
58. The disappearance of spindle and uncoiling of Thus (a) is correct option.
chromosomes takes place in:
(a) Anaphase (b) Telophase 62. ______ is not a stage of mitosis.
(c) Pachytene (d) Meiosis (a) prophase (b) Interphase
(c) Metaphase (d) Anaphase
Ans : SQP 2018
Ans : COMP 2010
Telophase is the fifth and final phase of mitosis.
During telophase, the chromosomes begin to Interphase is technically not part of mitosis, but
uncoil, the spindle breaks down, and the nuclear rather encompasses stages G1, S, and G2 of the
membranes and nucleoli reform. The cytoplasm cell cycle. In interphase, the cell is engaged in
of the mother cell divides to form two daughter metabolic activity and prepares for mitosis.
cells, each containing the same number and kind Thus (b) is correct option.
of chromosomes as the mother cell.
Thus (b) is correct option. 63. The period between two successive mitotic
divisions is :
59. A duplicated chromosome has ______ (a) Diakinesis (b) Interphase
chromatids (c) Anaphase (d) Mitosis
(a) One (b) Two Ans : SQP 2004
(c) Three (d) Four
The period between two successive mitotic
Ans : COMP 2004 divisions is interphase. It is also called resting
A single part of the duplicated chromosome is phase and includes all the changes that takes
known as the chromatid which is separated during place in a newly formed cell before it becomes
the cell division and each cell gets one chromatid. capable of division.
Thus, the duplicated chromosome has two sister Thus (b) is correct option.
chromatids.
Thus (b) is correct option. 64. Lateral pairing of homologous chromosomes is
known as ______
60. Mitosis is characterised by ______ (a) Recombination (b) Chiasmata
(a) Reduction division (c) Cross over (d) Synapsis
(b) Equal division Ans : COMP 2007
(c) Both reduction and equal division
(d) Pairing of homologous chromosomes Synapsis is the pairing of two chromosomes that
occurs during meiosis. It allows matching-up of
Ans : SQP 2009 homologous pairs prior to their segregation and
Mitosis is characterised by equal division because possible chromosomal crossover between them.
the chromosome number in the daughter cells Synapsis takes place during prophase I of meiosis.
remain same as that of parent cell. Thus (d) is correct option.
Thus (b) is correct option.
ICSE CHAPTERWISE PYQ CLASS 10 BIOLOGY PAGE 17

65. The period of rest between two successive cell of gametes through reductional division which
divisions is ______ result in halving of the number of chromosomes.
(a) Karyokinesis Meiosis results in the formation of gametes.
(b) Interphase Thus (d) is correct option.
(c) Prophase
(d) Dikaryophase 69. Centromere is concerned with ______.
(a) Duplication of DNA
Ans : MAIN 2019
(b) Formation of spindle fibres
The period between two successive cell divisions (c) Splitting of chromosomes
is called interphase or the resting phase. (d) Replication of DNA
Thus (b) is correct option. Ans : SQP 2017

66. In complementary base pairing of DNA, guanine A centromere is a region of DNA that is
always pairs with ______ and adenine always responsible for the movement of the replicated
pairs with ______. chromosomes into the two daughter cells by
(a) Cytosine, uracil splitting of chromosomes.
(b) Cytosine, thymine Thus (c) is correct option.
(c) Thymine, cytosine
(d) Guanine, adenine 70. The nuclear membrane disappears completely
during ______
Ans : COMP 2021
(a) Early prophase
The four nitrogenous bases of DNA are thymine, (b) Later prophase
adenine, guanine and cytosine. Guanine and (c) Metaphase
cytosine are bound together by three hydrogen (d) Telophase
bonds; whereas, adenine and thymine are bound Ans : MAIN 2002
together by two hydrogen bonds. This is known as
complementary base pairing. Nuclear membrane starts disappearing at the start
Thus (b) is correct option. of mitosis and by the late prophase it disappears
completely along with the major cell organelles.
67. A pair of corresponding chromosomes of the same Thus (b) is correct option.
shape and size but one from each parent.
(a) Autosomes 71. Network of long, thin, dark staining fibres seen in
(b) Sex chromosomes the interphase nucleus is ______
(c) Homologous chromosomes (a) Synapsis
(d) Analogous chromosomes (b) Chromatin fibres
(c) Nucleosome
Ans : SQP 2002
(d) Nucleotide
Homologous chromosomes are a pair of Ans : SQP 2006
corresponding chromosomes of the same shape,
size and length containing the same genes in In inter-phase, the nucleus shows a network of
the same order, one from each parent. During very long extremely thin dark staining fibres
fertilisation if pairing between sex chromosomes called as chromatin fibres. Chromosomes are the
of same shape and size occurs such pairing is high condensed coiled chromatin fibres.
called homologous pairing and chromosomes are Thus (b) is correct option.
called homologous chromosomes.
72. Cells which are not dividing are likely to be at
Thus (c) is correct option.
______
68. Meiosis in diploid organisms results in ______ (a) G 1 (b) G 2
(a) Production of gametes (c) G o (d) S phase
(b) Reduction in the number of chromosomes Ans : COMP 2012
(c) Introduction of variation
Cells that do not divide further exit G 1 phase to
(d) All of the above
enter an inactive stage and called quiescent stage
Ans : MAIN 2008 G o of the cell cycle.
Meiosis is cell division responsible for production Thus (c) is correct option.
CH 1 : CELL CYCLE AND STRUCTURE OF CHROMOSOMES

73. Spindle Fibres description?

(a) Helps to divide the nucleus equally in the
daughter cells from the parent cell.
(b) Helps to divide the cytoplasm in the daughter
cells from the parent cell.
(c) Helps to divide the chromosome equally in
the daughter cells from the parent cell.
(d) Helps to divide the centrosome equally in the
daughter cells from the parent cell.
Ans : SQP 2005
(a) Anaphase, as chromatids are being pulled
Spindle fibres helps to divide the chromosome towards the opposite poles.
equally in the daughter cells from the parent cell (b) Metaphase, as chromosomes are in the
during both types of nuclear division: mitosis and equatorial plane.
meiosis. (c) Anaphase, as chromosome gets attached to
Thus (c) is correct option. spindle by its centromere.
74. Given below is a diagram representing a stage (d) Telophase, as the chromatids has reached the
during the mitotic cell division. Which one of the two poles.
following option is the correct stage? Ans : SQP 2004

During anaphase the centromeres divide and the

chromatids start moving towards the two opposite
poles.
Thus (a) is correct option.

77. Chromosomes
(a) Thread-like structure found in DNA that
carry genetic information of an organism in
the form of genes.
(a) Prophase (b) Metaphase (b) Ring-like structure found in RNA that carry
(c) Anaphase (d) Telophase genetic information of an organism in the
Ans : SQP 2001
form of genes.
(c) Thread-like structure found in both DNA
During telophase, Chromosome sets assemble and RNA that carry genetic information of
at opposite poles, a nuclear envelope reforms an organism in the form of genes.
around each set and cytokinesis (division of the (d) Thread-like structure found in RNA that
cytoplasm) usually follows. carry genetic information of an organism in
Thus (d) is correct option. the form of genes.
75. Ribosomes Ans : SQP 2014
(a) Scattered inside the cell Chromosomes are thread-like structure found in
(b) Scattered inside the plasma membrane DNA that carry genetic information of an organism
(c) Scattered inside the nucleus in the form of genes. Different organisms have
(d) Scattered in the cytoplasm different numbers of chromosomes. Humans have
Ans : MAIN 2007 23 pairs of chromosomes–22 pairs of numbered
chromosomes, called autosomes, and one pair of
Ribosomes are small granules which are found
sex chromosomes, X and Y.
scattered in the cytoplasm. They are single walled
Thus (a) is correct option.
spherical bodies composed mainly of RNA.
Thus (d) is correct option. 78. Chromosomes
(a) The carriers of heredity
76. Given below is a diagram representing a stage
(b) The controlling centre of the cell
during the mitotic cell division. Which one of the
(c) The site for various chemical reactions
following option is the correct stage as per the
(d) Intracellular digestion.
ICSE CHAPTERWISE PYQ CLASS 10 BIOLOGY PAGE 19
Ans : SQP 2023
They give instructions for a living being to make
Chromosomes are the carriers of heredity which molecules called proteins. In other words, they
means they are responsible to provide hereditary encode particular protein which express in the
characteristics and genetic information to the form of some particular feature of the body.
various cells. Thus (c) is correct option.
Thus (a) is correct option.
83. Nucleus
79. Spindle fibres (a) Centre of the cytoplasm
(a) Between the two centrioles (b) Between the cell membrane and cytoplasm
(b) Between the two centrosomes (c) Equator of the cell
(c) Between chromatid and centromere (d) Between nucleolus and cell membrane
(d) Between two centromeres
Ans : COMP 2010
Ans : MAIN 2018
Nucleus is a large spherical body found at the
They appear between the two daughter centrioles centre of the cytoplasm. It regulates all the cell
and is necessary to equally divide the chromosomes function.
in a parental cell into two daughter cells during Thus (a) is correct option.
both types of nuclear division mitosis and meiosis.
Thus (a) is correct option. 84. Centromeres.
(a) It is a part of nucleus through which
80. Cytoplasm. chromosomes are linked.
(a) Inside the cell between the nucleolus and the (b) It is a part of chromosome through which
centromere chromatids are linked.
(b) Inside the cell between the nucleus and the (c) It is a part of DNA through which chromatids
cell membrane are linked.
(c) Inside the cell between the mitochondria and (d) It is a part of RNA through which
the cell membrane. chromosomes are linked.
(d) Inside the cell near to the cell membrane
Ans : COMP 2006
Ans : MAIN 2001
Centromere is a structure in a chromosome that
Cytoplasm is located inside the cell between the holds together the two chromatids (the daughter
nucleus and the cell membrane. It comprises gel- strands of a replicated chromosome).
like substance called cytosol and the various cell Thus (b) is correct option.
organelles (the cell’s internal sub-structures).
Thus (b) is correct option. 85. Meiosis
(a) A process where a single cell divides twice to
81. Chromosomes produce four cells containing half the original
(a) In the cytoplasm of plant and animal cell. amount of genetic information.
(b) In the centrosome of plant and animal cell. (b) A process where a nucleus divides twice to
(c) In the RNA of plant and animal cell. produce four cells containing the original
(d) In the nucleus of plant and animal cell. amount of genetic information.
(c) A process where a cell divides thrice to
Ans : COMP 2010
produce four cells containing half the original
Chromosomes are thread like structures located amount of genetic information.
inside the nucleus of animal and plant cells. Each (d) A process where a DNA divides twice to
chromosome is made of protein and a single produce eight cells containing half the original
molecule of deoxyribonucleic acid (DNA). amount of genetic information.
Thus (d) is correct option.
Ans : MAIN 2020
82. Genes Meiosis is a process where a single cell divides
(a) Help in carrying gametes twice to produce four cells containing half the
(b) Encode fats and lipids original amount of genetic information. These
(c) Encode particular protein cells are sex cells i.e., sperms in males and eggs
(d) Help in DNA replication in females.
Ans : MAIN 2007 Thus (a) is correct option.
CH 1 : CELL CYCLE AND STRUCTURE OF CHROMOSOMES

86. Gene What is the diploid number for this organism?

(a) Physical and functional unit of heredity that (a) 10 (b) 20
carries DNA material from one generation to (c) 40 (d) 46
the next.
Ans : COMP 2017
(b) Physical and functional unit of heredity that
carries chromosomes from one generation to The haploid number is exactly half the total
the next. number of chromosomes present in the organism’s
(c) Physical and functional unit of heredity that somatic cells and results due to reduction division
carries gametes from one generation to the next. (meiosis). As the nucleus contains 20 chromosomes
(d) Physical and functional unit of heredity the diploid number will be twice that of the
that carries genetic information from one haploid cell, i.e., 40.
generation to the next. Thus (c) is correct option.

Ans : COMP 2022 89. In the following diagram of a section of a DNA

The fundamental unit of heredity that carries molecule, what is the part labelled Q?
genetic information from one generation to the next.
A gene is an ordered sequence of nucleotides located
on a particular position on a particular chromosome
that encodes a specific functional protein.
Thus (d) is correct option.

87. Mitosis
(a) A process of cell replication during which one
cell gives rise to two non-identical daughter cells.
(b) A process of fission of cell during which one
cell gives rise to three genetically identical
daughter cells.
(c) A process of nuclear division during which
one cell gives rise to two genetically identical
daughter cells.
(d) A process of cell division during which one
cell gives rise to four genetically identical
(a) Adenine (b) Cytosine
daughter cells.
(c) Thymine (d) Uracil
Ans : MAIN 2000
Ans : SQP 2001
Mitosis, a process of nuclear division during which
In base pairing, adenine always pairs with
one cell gives rise to two genetically identical
thymine, and guanine always pairs with cytosine.
daughter cells. It has four stages prophase,
Thus (b) is correct option.
metaphase, anaphase and telophase.
Thus (c) is correct option. 90. The diagram given below represents a stage during
cell division. Which stage is depicted and name
88. The diagram shows a cell of an organism formed
the stage that comes before the stage shown?
by reduction division. The nucleus contains 20
chromosomes
ICSE CHAPTERWISE PYQ CLASS 10 BIOLOGY PAGE 21

(a) Metaphase, Prophase enzymes, hormones etc.

(b) Metaphase, Anaphase Thus (b) is correct option.
(c) Anaphase, Metaphase
(d) Anaphase, Telophase 93. DNA
(a) Controls functioning of RNA
Ans : SQP 2009
(b) Controls biosynthetic processes of cell.
Metaphase is marked by the arrangement of (c) Stores all of the genetic information
chromosomes on the equator of spindle. Prophase (d) Controls mitotic and meiotic division.
is the stage which comes before Metaphase. Ans : MAIN 2010
Thus (a) is correct option.
The function of DNA is to store all of the genetic
91. The diagram shows the formation of new diploid information that an organism needs to develop,
cells. function and reproduce.
Thus (c) is correct option.

94. The diagram shows a cell of an organism. The

nucleus contains 12 chromosomes.

What do arrows X and Y represent?

X Y
After it divides by mitosis, how many chromosomes
(a) Duplication of merosis
would be present in one of the daughter cells?
chromosomes
(a) 6 (b) 12
(b) Duplication of merosis (c) 18 (d) 24
chromosomes
Ans : COMP 2007
(c) Meiosis duplication of
During mitosis, a cell duplicates all of its contents,
chromosomes
including its chromosomes, and splits to form two
(d) Mitosis duplication of identical daughter cells with the same number of
chromosomes chromosomes.
At the end of mitosis, the two daughter cells will
Ans : COMP 2013
be exact copies of the original cell. Each daughter
In mitosis, chromosome duplication occurs during cell will have 12 chromosomes.
interphase. Mitosis is a part of the cell cycle in Thus (b) is correct option.
which replicated chromosomes are separated into
two new nuclei. 95. The diagram shows stages of meiosis in a human
Thus (b) is correct option. testis:

92. Golgi Apparatus

(a) Synthesis of respiratory enzymes
(b) Synthesis and secretion of enzymes, hormones
etc.
(c) Synthesis of Protein.
(d) Regulates cell function
Ans : SQP 2017

Golgi apparatus are stacks of flattened membrane

sacs that helps in the synthesis and secretion of
CH 1 : CELL CYCLE AND STRUCTURE OF CHROMOSOMES

After meiosis I After meiosis II

(a) 46 46
(b) 46 23
(c) 23 46
(d) 23 23

Ans : SQP 2015

A human cell has 46 total or 23 pairs of

chromosomes. The first division is called the
reduction division or meiosis
I — because it reduces the number of chromosomes
from 46 chromosomes or 2n to 23 chromosomes
or n. Meiosis II resembles a mitotic division, and
after meiosis II, 23 chromosomes results.
Thus (d) is correct option.

96. In the diagram given below of a section of a DNA

molecule, which are the two components of part X?

(a) Ribose and Phosphate

(b) Guanine and Phosphate
(c) Deoxyribose and Thymine
Ans : MAIN 2000
(d) Deoxyribose and Phosphate
The DNA in the cell is copied in preparation for
Ans : COMP 2009
cell division during interphase or a stage before
The backbone of a DNA molecule consists of the the start of mitosis. This results in two identical
phosphate groups and the deoxyribose sugars, full sets of chromosomes.
whereas the base region of the DNA molecule Thus (a) is correct option.
consists of the nitrogenous bases; therefore, the
backbone of DNA is made up of phosphate groups
and pentose sugars. Adenine is part of the base
region of the molecule. DNA does not contain any ASSERTION AND REASON
hexose (six-carbon) sugars.
Thus (d) is correct option.
98. Assertion : G1 phase is the interval between
97. The diagram shows a cell before and during mitosis and initiation of DNA replication.
mitosis. At which stage are the chromosomes Reason : The cell is metabolically inactive during
copied? G1 phase.
ICSE CHAPTERWISE PYQ CLASS 10 BIOLOGY PAGE 23

(a) If both assertion and reason are true and are formed which remain attached in pairs and
reason is the correct explanation of assertion. the number of chromosomes does not increase. As
(b) If both assertion and reason are true, but the chromatin fibres are elongated chromosomes,
reason is not the correct explanation of each chromosome comes to have two chromatin
assertion. threads which are attached at centromere. During
(c) If assertion is true but reason is false. metaphase, every chromosome has two chromatids
(d) If both Assertion and Reason are false. which separate from each other during anaphase.
Thus (a) is correct option.
Ans : SQP 2014

G1 phase is also known as first growth phase 101. Assertion : During anaphase, centromere of each
or post mitotic gap phase. It is the phase chromosomes splits and chromatids separate.
between end of mitotic phase of previous cell Reason : Chromatids move to opposite poles.
and initiation of S-phase of next mitotic phase. (a) If both assertion and reason are true and
During G1 phase, the cell is metabolically active reason is the correct explanation of assertion.
and continuously grows. RNA and proteins are (b) If both assertion and reason are true, but
synthesized. Organelle duplication such as those reason is not the correct explanation of
of mitochondria and chloroplast also occurs assertion.
during this phase. (c) If assertion is true but reason is false.
Thus (c) is correct option. (d) If both Assertion and Reason are false.

99. Assertion : The M phase represents the phase Ans : SQP 2012

when the actual cell division occurs. During anaphase the centromeres divide and
Reason : Interphase represents the phase between the chromatids start moving towards the two
two successive M Phase. opposite poles. Spindle fibres attached to the
(a) If both assertion and reason are true and centromeres shorten and pull the chromosomes;
reason is the correct explanation of assertion. the centromeres lead the path while the limbs trail
(b) If both assertion and reason are true, but behind. Anaphase ensures that each chromosome
reason is not the correct explanation of receives identical copies of the parent cell’s DNA.
assertion. Thus (b) is correct option.
(c) If assertion is true but reason is false.
(d) If both Assertion and Reason are false. 102. Assertion : Mitosis maintains the genetic similarity
of somatic cells.
Ans : COMP 2019
Reason : Chromosomes do not undergo crossing
The M phase represents the phase when the over.
actual cell division occurs. Interphase represents (a) If both assertion and reason are true and
the phase between two successive phases. reason is the correct explanation of assertion.
Thus (b) is correct option. (b) If both assertion and reason are true, but
reason is not the correct explanation of
100. Assertion : Every chromosome, during metaphase
assertion.
has two chromatids.
(c) If assertion is true but reason is false.
Reason : Synthesis of DNA takes places in the
(d) If both Assertion and Reason are false.
S-phase of interphase.
(a) If both assertion and reason are true and Ans : SQP 2017

reason is the correct explanation of assertion. Mitosis keeps all the somatic cells of an organism
(b) If both assertion and reason are true, but genetically similar, resembling the fertilized
reason is not the correct explanation of egg. Mitosis involves replication and equitable
assertion. distribution of all the chromosomes so that all the
(c) If assertion is true but reason is false. cells of a multicellular organism have the same
(d) If both Assertion and Reason are false. number and type of chromosomes.
Ans : MAIN 2022 During the formation of gametes by meiosis,
paired chromosomes from each parent align so
In S phase or synthesis phase, chromosomes
that similar DNA sequences from the paired
replicates, DNA content doubles, i.e., 1C to 2C for
chromosomes cross over one another. Crossing
haploid cells and 2C to 4C for diploid cells. Along
over results in a shuffling of genetic material and
with replication of DNA, new chromatin fibres
CH 1 : CELL CYCLE AND STRUCTURE OF CHROMOSOMES

is an important cause of the genetic variation seen Reason: Interphase (I-phase) is the long non-
among offspring. dividing phase.
Thus (a) is correct option. (a) If both assertion and reason are true and
reason is the correct explanation of assertion.
103. Assertion : In animal cells, cytokinesis is (b) If both assertion and reason are true, but
marked by the appearance of a furrow in plasma reason is not the correct explanation of
membrane. assertion.
Reason : In plant cells, the formation of the (c) If assertion is true but reason is false.
new cell wall starts with the formation of simple (d) If both Assertion and Reason are false.
precursor called cell Plate.
(a) If both assertion and reason are true and Ans : SQP 2011

reason is the correct explanation of assertion. The cell cycle is divided into two basic phase:
(b) If both assertion and reason are true, but (i) interphase, (ii) M-phase.
reason is not the correct explanation of The M phase represents the phase when the actual
assertion. cell division or mitosis occurs and the interphase
(c) If assertion is true but reason is false. represents the phase between two successive M
(d) If both Assertion and Reason are false. phases. In the 24 hour average duration of cell
Ans : SQP 2004
cycle of human cell, cell division proper lasts for
only about an hour. The interphase lasts more
In an animal cell, cytokinesis is marked by the than 95% of the duration of cell cycle during
appearance of a furrow in the plasma membrane which the cell grows and DNA is replicated.
which gradually deepens and ultimately joins in Thus (b) is correct option.
the centre dividing the cell cytoplasm into two.
As plants cells are enclosed by a relatively 106. Assertion : Karyokinesis occurs in M-phase.
inextensible cell wall they undergo cytokinesis by Reason : Cell division stops in M-phase.
a different mechanism. New cell plates are formed (a) If both assertion and reason are true and
at the equator, which extend from centre to the reason is the correct explanation of assertion.
periphery (centrifugal) until the cell divides into (b) If both assertion and reason are true, but
two daughter cells. reason is not the correct explanation of
Thus (b) is correct option. assertion.
(c) If assertion is true but reason is false.
104. Assertion: Genes are specific sequences of (d) If both Assertion and Reason are false.
nucleotides on a chromosome.
Reason: A nucleotide is made up of nitrogenous Ans : MAIN 2007

base, a phosphate group and a pentose sugar. M-phase represents the phase of actual division.
(a) If both assertion and reason are true and It consists of karyokinesis (the division of nucleus)
reason is the correct explanation of assertion. followed by cytokinesis (the division of cytoplasm).
(b) If both assertion and reason are true, but Cell division continues throughout the M-phase
reason is not the correct explanation of and after the M-phase is completed cell division
assertion. ceases (stops).
(c) If assertion is true but reason is false. Thus (d) is correct option.
(d) If both Assertion and Reason are false.
Ans : MAIN 2016

Genes are made up of DNA and each chromosome

contains many genes. Genes are specific sequences ONE MARK QUESTIONS
of nucleotides on a chromosome. A nucleotide has
three components: a nitrogenous base, a pentose
sugar (deoxyribose for DNA), and a phosphate DIRECTION : Name the following :
group.
Thus (b) is correct option. 107. Acts as bearer of heredity units.
105. Assertion: Interphase occupies 75-95% of the Ans : MAIN 2002
total generation time. Chromosomes
ICSE CHAPTERWISE PYQ CLASS 10 BIOLOGY PAGE 25

108. A pair of corresponding chromosomes of the same Mitosis

shape and size and derived one from each parent.
118. The stage when sister chromosomes separate from
Ans : SQP 2018, 2017
the paired condition.
Homologous Chromosome Ans : SQP 2005

109. The number of chromosomes present in a nerve Meiosis

cell of a human being.
119. The structure which initiates cell division in
Ans : COMP 2018
animal cells.
46 Ans : MAIN 2001

110. A region of plant body where cell division occurs Centrosome

very actively.
120. The point at which the duplicated chromosomes
Ans : SQP 2002, 1995
are joined.
Growing points (Apical meristem) such as tips of Ans : COMP 2010
root and stems.
Centromere
111. Chromosomes appear thread like.
121. The largest phase of a normal cell cycle.
Ans : COMP 2009
Ans : MAIN 2000
Telophase
Prophase
112. The type of cell division which occurs in the cells
of the reproductive organs. 122. The shortest phase of mitosis.

Ans : MAIN 2010

Ans : COMP 2008

Meiosis Anaphase

113. The exchange of chromatid parts between the 123. The points of attachment where crossing over
maternal and the paternal chromatids of a pair of occurs.
homologous chromosomes during meiosis. Ans : MAIN 2003

Ans : SQP 2016 Chiasmata

Crossing over
124. The type of cell division that occurs in unicellular
114. A nitrogenous base in DNA. organisms.

Ans : MAIN 2022

Ans : SQP 2015

Adenine Amitosis

115. The two kinds of cell division found in living 125. Division of nucleus.
organisms. Ans : MAIN 2009

Ans : COMP 2023 Karyokinesis

Mitosis and Meiosis
126. Division of cytoplasm.
116. Name the stage during which nuclear membrane Ans : COMP 2016
and nucleolus reappear.
Cytokinesis
Ans : SQP 2018
127. The stage when chromosomes arrange at the
Telophase
equator.
117. The kind of division normally seen at the tip of Ans : SQP 2007
root and shoot system.
Metaphase
Ans : MAIN 2014
CH 1 : CELL CYCLE AND STRUCTURE OF CHROMOSOMES

128. A membrane that disappears during late prophase. Ans : SQP 2018

Ans : SQP 2023

nucleus

Nuclear membrane. 138. The direct cell division is called as______.

129. The structure responsible to transmit Ans : COMP 2011

characteristics from parent to offspring. amitosis

Ans : MAIN 2000
139. The chromosome number is______in meiosis.
Chromosome
Ans : MAIN 2003

130. The specific part of a chromosome that determines reduced

hereditary characteristics.
140. The paired homologous chromosomes of the
Ans : COMP 2021
zygotene stage are called______.
DNA
Ans : SQP 2017

131. The kind of cell division which occur in pollen bivalents

grains.
141. The process by which cell multiply is
Ans : MAIN 2012
called______.
Meiosis
Ans : SQP 2004

132. What are chromosomes ? cell division

Ans : SQP 2019
142. In______of interphase, RNA and proteins are
The chromosomes are fine thread like structures synthesised.
found in the nucleus of both plant and animal
Ans : MAIN 2007
cells.
G1 - phase

DIRECTION : Complete the following: 143. Condensation of chromosome with centromere

occurs in______of interphase.
133. The region of the attachment of chromosomes to Ans : MAIN 2001
spindle fibres is at______.
S-phase
Ans : COMP 2014

Centromere DIRECTION : State true/false And if the statement

is false than write the correct statement :
134. Exchange of genetic materials between non-sister
chromatids is called______.
144. Mitosis is the type of cell division occurring in the
Ans : MAIN 2000 cells of injured parts of the body.
crossing over Ans : SQP 2010

135. ______is the pairing of chromosomes during True

zygotene.
145. Lysosomes is a part of the cell in which
Ans : COMP 2008 chromosomes are present.
Synapsis Ans : MAIN 2011

False. Nucleus is a part of cell in which

136. Replication of DNA occurs in the______of chromosomes are present.
interphase.
Ans : MAIN 2020
146. Centromere is the organelle of the cell that
initiates cell division.
S-phase Ans : COMP 2011

137. Karyokinesis is the division of______. True

ICSE CHAPTERWISE PYQ CLASS 10 BIOLOGY PAGE 27

147. The points at which crossing over has taken place 156. Choose the correct answer :
between homologous chromosomes are called Duplicated chromosomes are joined at a point
centromere. termed
(centrosome, centromere, centriole, chromatid).
Ans : SQP 2017

False. The points at which crossing over has Ans : MAIN 2002

taken place between homologous chromosomes Centromere

are called chiasma.

148. Mitosis is called reduction division. DIRECTION : Fill in the blanks with suitable words:

Ans : SQP 2010

157. The chromosome number in our skin cell
False. Meiosis is called reduction division. is______.

149. Four daughter cells are formed as a result of Ans : MAIN 2019

meiosis. 46
Ans : COMP 2021
158. The spindle fibres are made-up of______.
True.
Ans : COMP 2015

150. During anaphase, chromosomes are arranged at Microtubules

the equator.
159. The process by which gametes are formed is
Ans : MAIN 2014
called______.
False. During anaphase, chromosomes are
Ans : COMP 2006
arranged at the poles.
Gametogenesis (Meiosis)
151. During telophase, the nuclear membrane
disappears. 160. The direct cell division is called as______.

Ans : COMP 2002 Ans : MAIN 2009

False. During telophase, the nuclear membrane Amitosis

reappears.
161. In meiosis, the parent cell is diploid whereas the
152. The number of pairs of autosomes in man is 22. daughter cell is______.

Ans : MAIN 2000 Ans : COMP 2018

True. Haploid

153. Lysosome is a part of the cell in which chromosomes 162. By the end of prophase, chromosomes are seen as
are present. thick rods each having two rods called______
chromatids.
Ans : SQP 2015
Ans : SQP 2001
False. Nucleus is a part of the cell in which
chromosomes are present. Sister

154. The resting stage in mitosis is called interphase. 163. The chromosomes which are exactly similar and
bear same genes at same loci are called______
Ans : MAIN 2023
chromosomes.
True.
Ans : MAIN 2007

155. Duplicated chromosomes remain attached at a Homologous

point termed centrosome.
164. The chromosome number is______in meiosis.
Ans : COMP 2020
Ans : COMP 2021
False. Duplicated chromosomes remain attached
at a point termed centromeres. Halved
CH 1 : CELL CYCLE AND STRUCTURE OF CHROMOSOMES

165. The process by which cell multiplies is 173. The exchange of chromatid parts between the
called______. maternal and the paternal chromatids of a pair of
homologous chromosomes during meiosis.
Ans : SQP 2004

Cell division Ans : MAIN 2016

Crossing over
166. The chromosomes move to the opposite poles
in______stage. 174. The kind of division that takes place in the
reproductive tissues.
Ans : COMP 2017

Anaphase Ans : COMP 2010

Anaphase
167. Meiosis I is also known as______division.
175. The repeating components of each DNA strand
Ans : MAIN 2001
lengthwise.
Reductional
Ans : SQP 2016

Deoxyribonuleotide
DIRECTION : Choose the ODD one out from the
following terms given and name the CATEGORY to 176. An alteration in the genetic material that can be
which the others belong: inherited.
Example : Nose, Tongue, Arm, Eye Ans : COMP 2016
Answer : Odd Term - Arm, Category - Sense
organs Mutation

168. Centrosome, Cell wall, Cell membrane, Large

DIRECTION : Distinguish between the following on
vacuoles
the basis of what is given in the brackets:
Ans :
177. Karyokinesis and Cytokinesis. (explain the term)
Odd term - Centrosome, Category - Parts of plant
cell Ans : MAIN 2010

Karyokinesis is the division of the nucleus into

169. Phosphate, RNA, Sugar, Nitrogenous base
two daughter nuclei. There are mainly four steps
Ans : MAIN 2018 involved in karyokinesis and they are prophase,
RNA : Rest are components of DNA metaphase, anaphase and telophase.
Cytokinesis is the division of the cytoplasm to
form two daughter cells. It varies in plant and
DIRECTION : Give appropriate biological or
animal cells. Cytokinesis follows the karvokinesis.
technical terms for the following :
178. Mitosis and Meiosis. (number of daughter cells
170. The suppressed alleles of a gene. formed)
Ans : COMP 2017 Ans : COMP 2004
Recessive Mitosis – Two daughter cells are formed.
Meiosis – Four daughter cells are formed.
171. The complex consisting of a DNA strand and a
core of histones.
DIRECTION : Correct the following statements by
Ans : SQP 2018
changing the underlined words :
Nucleosome
179. Nitrogen bonds are present between the
172. Expand the following biological abbreviations
complementary nitrogenous bases of DNA.
DNA.
Ans : SQP 2018
Ans : SQP 2019
Hydrogen
Deoxyribonucleic acid
ICSE CHAPTERWISE PYQ CLASS 10 BIOLOGY PAGE 29

DIRECTION : Identify the odd one from a set of Ans : SQP 2004

four terms and name the category to which the other Prophase, metaphase, anaphase, telophase.
three belong.
DIRECTION : Match the following:
180. Thymine, Cytosine, Adenine, Pepsin.
Ans : COMP 2016 187. Column ‘B’ is a list of terms related to ideas in
Odd one: Pepsin column ‘A’. Match the term in column ‘B’ with
Category: Nitrogen base bases of DNA (thymine, the suitable idea given in column ‘A’.
cytosine, adenine). Column A Column B
181. Phosphate, RNA, Sugar, Nitrogenous base (i) Chromosomes (a) Anaphase
become arranged in
Ans : MAIN 2017
a horizontal plane at
Odd one: RNA the equator.
Category: Components of DNA
(ii) Daughter (b) Prophase
chromosomes move
DIRECTION : Rewrite the following terms into to opposite poles of
logical sequence: the spindle.

182. Karyokinesis, S-phase, cytokinesis, G-1 phase, (iii) Chromosomes (c) Telophase
G-2 phase. become visible as
fine, long threads.
Ans : MAIN 2012
(iv) Chromosomes lose (d) Metaphase
G-1 phase, S-phase, G-2 phase, karyokinesis,
their distinctiveness
cytokinesis.
and generally become
183. Interphase, Anaphase, Prophase, Telophase, transformed into
Metaphase chromatin network.

Ans : SQP 2018 Ans : SQP 2017

Interphase Prophase $ Metaphase $

Anaphase $ Telophase. Column A Column B
(i) Chromosomes (d) Metaphase
DIRECTION : Given below are groups of terms. In become arranged in
each group the first pair indicates the relationship a horizontal plane at
between the two terms. Rewrite and complete the the equator.
second pair on a similar basis. (ii) Daughter (a) Anaphase
Example: Oxygen : Inspiration : : Carbon dioxide: chromosomes move
Expiration to opposite poles of
the spindle.
184. Cytoplasm : Cytokinesis : : Nucleus :______
(iii) Chromosomes (b) Prophase
Ans : become visible as
Cytoplasm : Cytokinesis : : Nucleas : Karyokinesis. fine, long threads.

185. Adenine : Thymine : : Cytosine :______ (iv) Chromosomes lose (c) Telophase
their distinctiveness
Ans : COMP 2017
and gradually
Adenine : Thymine : : Cytosine : Guanine become transformed
into chromatin
186. Write the terms in correct order so as to be in network.
logical sequence:
Metaphase; telophase; prophase; anaphase.
CH 1 : CELL CYCLE AND STRUCTURE OF CHROMOSOMES

DIRECTION : State the differences between the 191. Cytokinesis in plant and animal cell
following pairs:
Ans : SQP 2002

188. Mitosis and Meiosis The differences between Cytokinesis in plant and
animal cell are as follows :
Ans : MAIN 2020

The differences between Mitosis ans Meiosis are Cytokinesis in plant Cytokinesis in
as follows : cell animal cell
(a) It starts with a cell Cell plate formation
Mitosis Meiosis plate formation. is absent. A
(a) It is an equational It is a reductional constriction furrow
division. division. forms in the middle
of cell membrane.
(b) Two diploid Four haploid
daughter cells are daughter cells are (b) It is centrifugal. It is centripetal.
formed. formed.
(c) Only one division Two divisions 192. Mitosis in animal and plant cell
occurs. occur. Ans : MAIN 2008

(d) It occurs in somatic It occurs in The differences between Mitosis in animal and
cells. reproductive cells. plant cell are as follows :

Mitosis in Animal Mitosis in Plant

189. Centrosome and Centromere Cell Cell
Ans : SQP 2023 (a) Centrosome is Centrosome is
present. absent.
The differences between Centrosome and
Centromere are as follows : (b) Asters and spindle Asters are not
formation occurs. formed.
Centrosome Centromere
(c) In telophase, In telophase, a cell
(a) It is an organelle of It is a point at cytoplasm constrict. plate is laid in the
the animal cell. which the duplicate cytoplasm at the
chromosomes are equatorial plane.
joined.
(b) It contains two It provides site 193. Asexual and Sexual Reproduction
centrioles which for attachment Ans : SQP 2001
move towards the of spindle fibres
opposite poles and during cell division. The differences between Asexual and Sexual
form spindle fibres Reproduction are as follows :
during cell division. Asexual Sexual
Reproduction Reproduction
190. Cytokinesis and Karyokinesis
(a) It is a type of Gametes are
Ans : COMP 2008 reproduction produced.
The differences between Cytokinesis and without gamete
Karyokinesis are as follows : formation.
(b) Variations are not Variations are
Cytokinesis Karyokinesis
produced. produced.
(a) It is the division of It is the division of
cytoplasm. nucleus. 194. S-phase and G2-phase
(b) It takes place after It is the first Ans : COMP 2009
Karkyokinesis. division. The differences between S-phase and G2-phase are
as follows :
ICSE CHAPTERWISE PYQ CLASS 10 BIOLOGY PAGE 31
Ans : MAIN 2000
S-phase G2-phase
A gene is a unit of heredity composed of DNA.
(a) Replication of DNA rRNA and mRNA
occurs in this phase. are synthesised in 202. What are the two forms of genes known as ?
this phase.
Ans : COMP 2017

(b) At this stage, the At this stage, the The two forms of genes are called alleles.
cell contains 2n of cell contains 4n of
DNA. DNA. 203. Where does Meiosis occur in our body ?
Ans : SQP 2021

Meiosis occurs in the reproductive organs (testis

DIRECTION : Answer the following :
and ovary) of our body.
195. What are the two divisions that follow during cell 204. What happens during metaphase of mitosis?
division ?
Ans : SQP 2011
Ans : MAIN 2000
During metaphase of mitosis, chromosomes are
Karyokinesis and cytokinesis. arranged at the equator.
196. How many meiotic divisions are necessary to 205. What is synapsis?
produce 100 pollen grains ?
Ans : MAIN 2018
Ans : COMP 2022
Synapsis is the pairing of homologous chromosomes.
25 meiotic divisions. It occurs in zygotene stage of meiosis I.
197. What is synapsis ?
Ans :
Pairing of homologous chromosomes during TWO MARKS QUESTIONS
zygotene stage of meiosis is called synapsis.

198. Name two animals which have nineteen pairs of 206. During Mitosis what is the position of chromatids
chromosomes. in:
(a) Metaphase
Ans : COMP 2004
(b) Anaphase
Lion ; Tiger.
Ans : SQP 2025

199. Write the names of four nitrogenous bases in a (a) In the equatorial plane
DNA molecule. (b) Sister chromatids separate and move towards
Ans : MAIN 2013 the opposite poles.

The four nitrogenous bases in a DNA molecule 207. Draw a well labelled diagram to show the
are : anaphase stage of mitosis in a plant cell having
1. Adenine four chromosomes.
2. Guanine
Ans : COMP 2005
3. Cytosine
4. Thymine

200. Give the specific function of Centrosome

Ans : SQP 2009

Centrosome initiates and regulates cell division

in animal cells by forming spindle fibres with the
help of asters.

201. What is a gene ?

CH 1 : CELL CYCLE AND STRUCTURE OF CHROMOSOMES

208. How is variation produced in a species ? 2. DNA is synthesized.

3. Cell increases in size.
Ans : MAIN 2001

During meiosis, exchange of genetic material 214. What is a sat chromosome ?

between non-sister chromatids occur resulting in Ans : SQP 2002
new combinations. These combinations give rise
to variation resulting in the evolution of species. Sometimes the chromosomes bear round,
elongated or knob like appendages known as
209. Why is the first division of meiosis called as satellites. The satellite remains connected to the
reductional division ? rest of the chromosomes with satellites are called
sat chromosomes.
Ans : SQP 2017

The first division of meiosis is called as reductional 215. The figure shows two types of chromosomes.
division because in this division the chromosome Identify them and give reason for your choice.
number is reduced to half.

210. Why do gametes have a haploid number of

chromosomes ?
Ans : COMP 2019

Gametes have a haploid number of chromosomes

in order to maintain the 2n chromosome of
diploid zygote, when they fuse together to form
the zygote. Ans : COMP 2009

A – Metacentric : The centromere is present in

211. State how does meiosis maintain the chromosome the centre and two arms of the chromatids are
number in a species? equal.
Ans : COMP 2023 B – Telocentric : The centromere is present at one
end of the chromosome.
The gametes are formed by meiosis during
which the number of chromosomes are reduced 216. What is the significance of mitosis?
to half, i.e gametes contain haploid number of
chromosomes. The male and female gametes fuse Ans : SQP 2015

to form a zygote. In this way meiosis maintains It helps in the growth, repair and development
the chromosome number in a species. of the body. It is a type of reproduction in
protozoans.
212. Name the type of cell division that occurs during :
(i) Growth of shoot 217. State the importance of meiosis.
(ii) Formation of pollen grains Ans : MAIN 2003
(iii) Repair of worn out tissues
The importance of meiosis are as follows :
Ans : SQP 2017 (i) It brings about variations in a species.
(ii) It maintains the chromosome number of a
(i) Mitosis
species.
(ii) Meiosis
(iii) It helps in evolution of species.
(iii) Mitosis
218. Name the cell division that takes place during
213. What is Interphase ? Mention Three significant
gametogenesis. What is its significance ?
changes that occur in a cell during Interphase.
Ans : SQP 2020
Ans : MAIN 2010
Meiosis occurs during gametogenesis.
In between two divisions, when a cell is resting or
Its significance is that it helps to restore the
non-dividing, the phase is called interphase. The
number of chromosomes of the species.
three significant changes that occur in cell during
interphase are : 219. Why is variation seen in progeny ?
1. Chromatin material duplicates.
Ans : COMP 2013
ICSE CHAPTERWISE PYQ CLASS 10 BIOLOGY PAGE 33

The exchange of the chromosome material Ans : MAIN 2019

during crossing over provides innumerable In a plant cell, a cell plate is formed between
recombinations because of which the off-springs the two daughter nuclei. It grows outwards and
of the same parents however similar are different ultimately touches the cell wall. It forms the
from each other in some respects. The variations middle lamella.
are one of the important cause of evolution.
227. What are the various ways in which pairing occurs
220. What is crossing over? during zygotene?
Ans : SQP 2010 Ans : SQP 2014

It is the process of exchange of genetic material Pairing may start from both the ends and move
between the non-sister chromatids of homologous towards the centre, it may start from the centre
chromosomes. It occurs during pachytene stage and move towards either end of the nucleus.
of meiosis.
228. What happens during prophase of mitosis?
221. How does meiosis maintain chromosome number?
Ans : COMP 2010
Ans : SQP 2005
During prophase, chromatin material starts
During meiosis, chromosome number in the cell condensing to form chromosomes. Each
is reduced to half. The gametes contain haploid chromosome contains two chromatids joined at
number of chromosomes. During fertilisation, the the centromere. Nuclear membrane and nucleolus
male and the female gametes fuse and form a disappears. Spindle fibres appear between the two
diploid cell. centrioles.

222. Meiosis is referred to as reduction division. Why? 229. Identify and name the following processes/terms
Ans : COMP 2000 from the statements given below:
(i) Chromosomes appear thread like.
Meiosis is called reduction division because
(ii) A pair of chromosomes carrying dissimilar
chromosome number reduces to half in daughter
alleles for a particular character.
cells.
Ans : COMP 2018
223. Why is meiosis essential in sexually reproducing
(i) Chromatin fibres.
organisms?
(ii) Heterozygous chromosomes.
Ans : MAIN 2008
230. Give reason: Gametes have a haploid number of
Meiosis helps to maintains a definite number of
chromosomes.
chromosomes in a species; crossing over which
occurs during meiosis produces variations. Ans : SQP 2020

Gametes are formed after meiosis. During meiosis,

224. What is a SAT chromosome?
reduction of the number of chromosomes occurs.
Ans : COMP 2012 So, during fertilisation the original number of
Sometimes a few chromosomes have a secondary chromosomes are retained.
constriction. The part of the chromosome beyond
231. State the functions of chiasmata.
the secondary constriction is called satellite. Such
chromosomes are called SAT chromosomes. Ans :. MAIN 2004

225. How does cytokinesis occur in an animal cell? The functions of chiasmata are as follows :
(i) Crossing over takes place at the chiasmata
Ans : SQP 2022 during meoisis.
In an animal cell, a cleavage/furrow appears (ii) To hold the homologous chromosomes
during telophase in the plasma membrane. This together prior to segregation.
furrow deepens and meets in the middle to form
232. What are the changes that occur during S-phase?
two daughter cells.
Ans : SQP 2012
226. How does cytokinesis occur in a plant cell?
S-phase: During this phase, replication of DNA
CH 1 : CELL CYCLE AND STRUCTURE OF CHROMOSOMES

takes place. Each chromosome contains two Figure A, is acrocentric; Figure B, is metacentric.
sister chromatids and are attached to a common In acrocentric chromosome, the centromere is
centromere. near to terminal region while in metacentric, the
centromere is in the centre of the chromosome.
233. Briefly explain the types of chromosomes
according to the positions of centromere.
Ans : COMP 2017

Based on the position of centromere, the THREE MARKS QUESTIONS

chromosomes are of four types:
1. Telocentric – It has a terminal centromere.
237. The given figure shows a cell. Study the figure
2. Acrocentric – Centromere is near to one end.
and then answer the questions that follow :
3. Submetacentric – Centromere is slightly away
(i) Identify the stage of cell cycle depicted by the
from the centre.
cell.
4. Metacentric – Centromere is in the middle.
(ii) Write any two characteristics of this phase.
234. What is DNA fingerprinting ? (iii) What are the main events which take place
when the cell goes into the next stage ?
Ans : SQP 2013

There are regions in between genes which are non-

functional. These areas/regions show tremendous
variation from individual to individual and are
peculiar from person to person. This technique is
commonly known as DNA fingerprinting.
or
It is a technique used to identify and analyse the
variations in various individuals at the level of
DNA. It is based on variability and polymorphism
in DNA sequences.
Now a days this technique is used to a great
extent in forensic science. Ans : MAIN 2009

235. The term ‘stem cells’ are often heard these days. (i) Inter-phase
Explain briefly of what it means. (ii) Inter-phase of a cell is characterized by :
1. Growth in cell size.
Ans : COMP 2017
2. Duplication of chromatin material and
Stem cells are biological cells that has the ability gets thinned and coiled up.
to differentiate into specialized cell types (mainly (iii) As the cell enters the next stage (Prophase)
into different tissues and organs). the following events take place :
They are generally found in multicellular 1. Centrioles become free and begin to move
organisms. towards the opposite poles.
2. Astral rays are developed and
236. The figure A and B show two types of chromosomes, chromosomes are seen.
identify them and write the difference. 3. Nuclear membrane and nucleolus starts
disappearing.

238. Try to guess the time period (in terms of days or

years) of how long the following cells last or are
replaced in human body.
(a) Liver cells
(b) Bone cells
(c) Epithelial cells of the gut
(d) Skin cells
Ans : COMP 2006 (e) RBC
(f) Eye, nerve and muscle cells
ICSE CHAPTERWISE PYQ CLASS 10 BIOLOGY PAGE 35
Ans : SQP 2007

(a) 300-500 days

(b) Every 10 years (approximately
(c) 5 days
(d) Every 14-15 days
(e) 120 days (approximately)
(f) Life time

239. The given figure represents a certain phenomenon

that occurs during meiosis:

241. Identify the stages of meiosis and label the parts

1 to 5.

(i) Name of the phenomenon. Ans : MAIN 2008

(ii) Define the phenomenon.
(iii) State the difference between chromosomes Anaphase-II
and chromatids. 1. Centriole;
2. Aster ray;
Ans : MAIN 2008 3. Spindle fibre;
(i) Crossing over. 4. Chromatid,
(ii) It is the exchange of genetic material between 5. Centromere
the non-sister chromatids of homologous
242. Draw the diagram of the following :
chromosomes.
(i) A cell cycle
(iii) Chromosomes are the carriers of heredity.
(ii) Telophase stage of mitosis in plant cell.
Chromatids are the two identical strands of a
duplicated chromosome. Ans : SQP 2017

240. With the help of neat sketches show how (i)

cytokinesis differs in a plant cell and in an animal
cell.
Ans : COMP 2013

(ii)
CH 1 : CELL CYCLE AND STRUCTURE OF CHROMOSOMES

shown in the diagram. Draw a neat labelled

diagram of the stage mentioned.
(v) Which is the cell division that results in half
the number of chromosomes in daughter cells?
Ans : COMP 2017

(i) Telophase.
The reasons are:
1. Two sets of daughter chromosomes are
seen on the opposite poles of the cell.
2. Reappearing of nuclear membrane and
nucleoli.
243. Draw a diagram of the nucleus of a cell, having 3. Formation of the chromatin fibres and
chromosome number 6, as it would appear in the deepening of cleavage furrow.
metaphase stage of mitosis and label the following (ii) 1. chromosomes
parts: 2. Nuclear membrane.
(a) Aster rays, (b) Acromatic spindle, (c) (iii) Karyokinesis.
Chromatid, (d) Centromere. (iv) Anaphase.
Ans : MAIN 2020

(v) Meiosis.

245. The diagram below represents a stage during cell

division. Study the same and then answer the
questions that follow :

FIVE MARKS QUESTIONS

244. Study the diagram given below which represents

a stage during the miotic cell division and answer
the questions that follow:

(i) Name the parts labelled 1, 2 and 3

(ii) Identify the above stage and give a reason to
support your answer.
(iii) Mention where in the body this type of cell
(i) Identify the stage giving suitable reasons.
division OMITS.
(ii) Name the parts numbered 1 and 2.
(iv) Name the stage prior to this stage and draw
(iii) What is the technical term for the division of
a diagram to represents the same.
nucleus?
(iv) Mention the stage that comes before the stage Ans : SQP 2011
ICSE CHAPTERWISE PYQ CLASS 10 BIOLOGY PAGE 37

(i) 1. Aster with astral rays (Centriole) 247. The diagram given below represents a certain
2. Spindle fibre and stage of mitosis:
3. Daughter chromosome.
(ii) Late Anaphase, as splitting of chromosome
takes place and daughter chromosome
proceeds towards the poles.
(iii) Somatic cells
(iv) Metaphase

(i) Identify the stage of cell division.

(ii) Name the parts labelled A and B.
(iii) What is the unique feature observed in this
stage?
(iv) How many daughter cells are formed from
this type of cell division?
246. There is a diagram of a double helical structure Ans : COMP 2015
of DNA: (i) The phase is Anaphase.
(i) Name the four nitrogenous bases that form a (ii) A – Spindle fibre
DNA molecule. B – Centromere/kinetochore
(ii) Give the full form of DNA. (iii) The unique feature is that the spindle fibres
(iii) Name the unit of heredity. are contracting and sister chromatids/
(iv) Mention two points of difference between daughter chromosomes are moving towards
Mitosis and Meiosis. the opposite poles of the cell.
(iv) Two daughter cells are formed from this type
of cell division.

248. The given diagram shows a stage during mitotic

division in an animal cell :
(i) Identify the stage. Give a reason to support
your answer.

Ans : COMP 2010

(i) Adenine, guanine, thymine and cytosine.

(ii) Deoxyribonucleic acid.
(iii) Genes.
(iv)

Mitosis Meiosis
(a) It occurs in the (a) It occurs in the (ii) Draw a neat labelled diagram of the cell as
somatic cells. reproductive it would appear in the next stage. Name the
cells. stage.
(b) Two daughter (b) Four daughter (iii) In what two ways is mitotic division in an
cells are formed. cells are formed animal cell different from the mitotic division
in a plant cell ?
CH 1 : CELL CYCLE AND STRUCTURE OF CHROMOSOMES

(iv) Name the type of cell division that occurs Spindle fibres.
during: (iii) The division of centromere helps in the
A. Growth of a shoot separation of two sister chromatids of each
B. Formation of pollen grains. chromosome, which are drawn apart towards
opposite poles.
Ans : SQP 2016
(iv) Metaphase
(i) Prophase-Nuclear membrane and nucleolus
disappear, chromatin resolve into
chromosomes.
(ii) Next stage is as shown below :

(iii) In animal cell, amphiastral spindle is formed 250. Given below is diagram representing a stage
whereas it is anastral spindle in the plant cells. during mitotic cell division. Study it carefully and
Secondly, in animal cells, cytokinesis takes answer the questions that follow:
place centripetally by constriction whereas in
plant cells, it is centrifugally by the formation
of cell plate.
(iv) A-Mitosis and B-Meiosis.

249. Given diagram representing a stage during mitotic

cell division in an animal cell :

(i) Is it a plant cell or an animal cell? Give a

reason to support your answer.
(ii) Identify the stage shown.
(iii) Name the stage that follows the one shown
here. How is that stage identified?
(iv) How will you differentiate between mitosis
(i) Identify the above stage. Give a reason to and meiosis on the basis of the chromosome
support your answer. number in the daughter cells?
(ii) Name the parts labelled 1, 2, 3 and 4. (v) Draw a duplicated chromosome and label its
(iii) What is the function of part 3? parts.
(iv) Name the stage that comes just after the
stage shown in the diagram. Draw a well Ans : COMP 2014

labelled diagram of this stage. (i) Plant cell:

Ans : MAIN 2010
1. It has cell wall.
2. Centrioles not present.
(i) Late prophase. Reason : Centrosome splits (ii) Prophase.
into two, occupying each pole, nuclear (iii) Metaphase. Chromosomes arrange themselves
membrane degenerating and chromosomes upon the equator of a spindle.
move towards the equator of the cell, spindle (iv) Mitosis – 46 chromosomes
fibres appear between two asters (centrioles). Meiosis – 23 chromosomes
(ii) 1. Astral rays 2. Chromatid 3. Centromere 4. (v)
ICSE CHAPTERWISE PYQ CLASS 10 BIOLOGY PAGE 39

252. The given diagram shows a stage during mitotic

division in an animal cell:
(i) Identify the stage. Give a reason to support
your answer.
(ii) Draw a neat labelled diagram of the cell as it
would appear in the next stage. Name the stage.
(iii) In what two ways is mitotic division in an
animal cell different from the mitotic division
in a plant cell?
(iv) Name the type of cell division that occurs
251. Given below is a diagram representing a stage during:
during the mitotic cell division. Study the diagram
and answer the following questions :

(i) Identify the stage by giving a suitable reason.

(ii) Is it a plant or an animal cell ? Give a reason
to support your answer. A. Growth of a shoot
(iii) Draw a neat, labelled diagram of the stage B. Formation of pollen grains.
which follows the one shown in the diagram.
Ans : COMP 2016
(iv) How many chromosomes will each daughter
cell have after the completion of the above (i) Prophase Reason – Nuclear membrane is
division ? disappearing.
(v) Name the four nitrogenous bases. (ii)
Ans : SQP 2019

(i) Anaphase : Two sister chromatids move

towards opposite poles.
(ii) Animal cell : No cell wall; presence of
centrioles at opposite poles.
(iii)

(iii)

Mitosis in plants Mitosis in

animals
(a) Asters are not (a) Asters are
formed due to formed.
lack of centrioles.
(b) Formation of (b) A constriction
cell plate in forms in the
(iv) Four telophase. cytoplasm in
(v) Adenine, Guanine, Cytosine, Thymine telophase.
(iv) A. Mitosis, B. Meiosis.
CH 1 : CELL CYCLE AND STRUCTURE OF CHROMOSOMES

253. Given is a diagram representing a stage during (iii) Name the type of cell division that occurs
mitotic cell division in an animal cell. during:
(i) Identify the stage. Give a reason to support 1. Replacement of old leaves by new ones.
your answer. 2. Formation of gametes.
(ii) Name the cell organelle that forms the aster. (iv) What is the stage that comes before the stage
(iii) Name the parts labelled 1, 2 and 3. shown in the diagram ?
(iv) Name the stage that follows this stage of (v) Draw a neat, labelled diagram of the stage
mitosis. How can this stage be identified? mentioned in above keeping the chromosome
number constant.
Ans : SQP 2012

(i) Animal cell : Centriole is present. [It can be a

plant cell also as it is double layered (cell wall
present) and astral rays are absent].
(ii) Metaphase : Unique feature is chromosomes
are arranged at the equatorial plate
(metaphasic) plate.
(iii) 1. Mitosis
2. Meiosis
(iv) Prophase
(v)

Ans : MAIN 2010

(i) Late prophase. The reason is that nuclear

membrane disappears.
(ii) Centrosome (centrioles).
(iii) 1. Centromere, 2. Chromosome, 3. Spindle
fibres
(iv) Metaphase. The chromosomes arrange
themselves on the equatorial or metaphase
plane.

254. The diagram given below represents a stage

during cell division.
Study the same and answer the questions that
follow : 255. Study the diagram given below which represents a
stage during the mitotic cell division and answer
the questions that follow :

(i) Identify the stage giving suitable reasons.

(i) Identify whether it is a plant cell or an animal (ii) Name the parts numbered 1 and 2.
cell. Give a reason in support of your answer. (iii) What is the technical term for the division of
(ii) Name the stage depicted in the diagram. nucleus?
What is the unique feature observed in this (iv) Mention the stage that comes before the stage
stage? shown in the diagram. Draw a neat labelled
ICSE CHAPTERWISE PYQ CLASS 10 BIOLOGY PAGE 41

diagram of the stage mentioned.

(v) Which is the cell division that results in half
the number of chromosomes in daughter cells?
Ans : SQP 2017

(i) The stage is Telophase. The reason is the

nucleus and nucleolus reappears and spindle
fibres disappeard.
(ii) 1. Centromere
2. Nuclear membrane/Nucleus
(iii) Karyokinesis
(iv) Anaphase (iii) Metaphase
(iv) Centromere/kinetochore
(v) Mitosis : Mitosis is a type of cell division in
which each chromosome of a parent cell splits
up longitudinally into two identical halves,
each half going to each of the daughter cell.

257. The figure shows a certain stage in cell division in

a cell with 4 chromosomes.

(v) Meiosis

256. The diagram represents the four stages of cell

division. Study the diagram carefully and then
answer the following questions :

(i) Name the parts labelled A and B.

(ii) What is C ? Give its function.
(iii) Name the type of division with a logic reason.
(iv) Name the stage before and the stage after the
stage shown in the diagram.
(i) What are the four stages of cell division ?
Ans : MAIN 2013
(ii) Label the various parts indicated after
rearranging the four stages in sequential (i) A is chromatid
order. B is centromere
(iii) In which stage the chromosomes undergo (ii) C is spindle to which chromosomes attach.
maximum condensation and arrange The spindle fibres pull the chromatids apart.
themselves in the equatorial plate ? (iii) Mitosis.
(iv) Name the structure by which the chromosomes The chromosomes line up on the spindle
get attached to the spindle fibres. singly. If it were meiosis the chromosomes
(v) Define the type of cell division that is would be in homologous pair.
represented in the above diagram. (iv) The stage before is interphase and the stage
after is metaphase.
Ans : COMP 2009

(i) 1. Prophase 258. Give one point of difference on the basis of what
2. Metaphase is given in the brackets:
3. Anaphase (i) Metacentric and Telocentric chromosomes
4. Telophase. –(Position of centromere)
(ii) (ii) Mitosis and Meiosis
–(Number of daughter cells formed)
CH 1 : CELL CYCLE AND STRUCTURE OF CHROMOSOMES

(iii) Maternal and Paternal chromosomes (ii) Name the parts labelled A, B, C and D.
–(Source) (iii) Where does this type of cell division usually
(iv) Chiasmata and Crossing over –(Function) occur?
(v) Mitosis in animal cell and Mitosis in plant cell (iv) Is the dividing cell shown as a plant or an
–(Telophase stage) animal cell? Give a reason to support your
answer.
Ans : MAIN 2002
Ans : SQP 2017
(i) Metacentric Telocentric (i) Anaphase.
chromosomes chromosomes (ii) A. Spindle fibre; B. Cell wall; C. Chromatid;
Centromere Centromere is D. Centromere.
is present in present at one end (iii) In the body (somatic) cells.
the centre of of chromosome. (iv) It is a plant cell as presence of cell wall, is
chromosome. shown clearly.
(ii) Mitosis Meiosis
Two daughter cells Four daughter cells
from one single from a single cell.
cell. CASE BASED QUESTION
(iii) Maternal Paternal
chromosomes. chromosomes
260. In living organisms, cell division is essential for
These These chromosomes
growth, development, repair, and reproduction.
chromosomes are are from father’s
Somatic (body) cells contain an even number of
from mother’s side. side.
chromosomes (2n). Mitosis ensures the creation of
(iv) Chiasmata Crossing over identical cells for growth and repair, while meiosis
It is the point of It is the exchange produces gametes with half the chromosome
attachment of non- of genetic material number, ensuring genetic diversity in sexually
sister chromatids between non- reproducing organisms.
of homologous sister chromatids 1. How does mitosis contribute to tissue repair?
chromosomes of homologous 2. Why is meiosis important for reproduction?
where crossing chromosomes. 3. What is the significance of an even number of
over takes place. chromosomes (2n) in somatic cells?
(v) Mitosis in animal Mitosis in plant cell 4. Briefly differentiate between mitosis and
cell In telophase stage, meiosis.
In telophase a cell plate is laid in Ans :
stage, cytoplasm the cytoplasm at the
1. Mitosis helps in tissue repair by producing
constricts. equatorial region.
identical cells to replace damaged ones.
2. Meiosis is crucial for reproduction as it halves
259. The diagram represents a stage in cell division. the chromosome number in gametes.
Study the same and answer the questions that 3. An even chromosome number ensures proper
follow: division and genetic stability in somatic cells.
4. Mitosis creates identical cells for growth,
while meiosis forms gametes for reproduction.

261. Interphase is a preparatory phase where the

cell grows, duplicates its DNA, and gets ready
for division. It is divided into three sub-stages:
G1 phase (cytoplasm increases, and proteins are
synthesized), S phase (DNA synthesis), and G2
phase (spindle proteins for mitosis are formed).
After completing interphase, the cell must divide
through mitosis.
(i) Identify the stage of cell division.
ICSE CHAPTERWISE PYQ CLASS 10 BIOLOGY PAGE 43

1 What happens to the chromatin material contain around 130,000 genes. While all body
during interphase? cells contain the same number of chromosomes
2. Describe the role of the G1 phase in interphase. and genes, some genes are active in all cells, like
Why is DNA synthesis important during the those involved in respiration. Others, like the gene
S phase of interphase? for insulin production, are only active in specific
3. What is the significance of the G2 phase in cells such as the beta cells of the pancreas.
preparing for mitosis? 1. What is the role of genes in heredity and
where are they located?
Ans :
2. Why are some genes active in all cells, while
1. The chromatin material duplicates during others are only active in specialized cells?
interphase due to DNA synthesis. 3. How many genes have scientists identified
2. In the G1 phase, the cytoplasm increases, and in human chromosomes, and what does this
protein synthesis occurs. suggest about genetic complexity?
3. DNA synthesis in the S phase is crucial for 4. Explain the function of the insulin-producing
duplicating genetic material before division. gene and where it is specifically active.
4. The G2 phase prepares the cell for mitosis by
synthesizing necessary spindle proteins. Ans :
1. Genes determine hereditary traits and are
262. Mitosis is the process where a single cell divides located in fixed positions on chromosomes.
to form two identical daughter cells. It consists of 2. Some genes are active in all cells for essential
two parts: karyokinesis (division of the nucleus) functions like respiration, while others, like
and cytokinesis (division of the cytoplasm). insulin genes, are active only in specialized
Karyokinesis includes four stages: prophase, cells.
metaphase, anaphase, and telophase. Afterward, 3. Scientists have identified about 130,000
cytokinesis splits the cytoplasm, completing the genes in human chromosomes, indicating the
cell division. complexity of genetic information.
1. What significant changes occur during 4. The insulin-producing gene is functionally
prophase in both animal and plant cells? active only in the beta cells of the pancreas.
2. What happens to the chromosomes during
metaphase and how is it significant? www.nodia.in
3. Explain how the chromatids behave in
anaphase and the result of this movement.
4. Describe the process of cytokinesis in animal
and plant cells.
Ans :
1. In prophase, chromosomes condense, spindle
fibers form, and the nuclear membrane
disappears in both plant and animal cells.
2. During metaphase, chromosomes align at the
equatorial plate, ensuring equal chromosome
distribution to daughter cells.
3. In anaphase, sister chromatids separate and
move to opposite poles, forming two groups
of chromosomes.
4. In animal cells, cytokinesis occurs through a
furrow, while in plant cells, a cell plate forms
to divide the cytoplasm.

263. Genes, which are specific parts of chromosomes

composed of DNA, determine hereditary traits and
are responsible for passing characteristics from one
generation to another. Each gene occupies a fixed
position in a chromosome. Human chromosomes