CLASS XII BIOLOGY (044) 2, NOV.2024.
Maximum Marks: 70 GT-02 Time: 3 hours
NCERT.
CH-1,2,3,8,9,10
General Instructions:
(i) All questions are compulsory.
(ii) The question paper has five sections and 33 questions. All questions are compulsory.
(iii) Section–A has 16 questions of 1 mark each; Section–B has 5 questions of 2 marks each;
Section– C has 7 questions of 3 marks each; Section– D has 2 case-based questions of 4 marks each;
and Section–E has 3 questions of 5 marks each.
(iv) There is no overall choice. However, internal choices have been provided in some questions. A
student has to attempt only one of the alternatives in such questions.
(v) Wherever necessary, neat and properly labeled diagrams should be drawn.
SECTION A
1. In heterogamous flowers, the male and female reproductive organs mature:
a) At the same time
b) On different flowers of the same plant
c) On different plants of the same species
d) In different seasons
2.
Identify A to G in following figure and answer
accordingly.
A) A-Ovary, B-Filament, C-Sepal, D-Petal, E-Style, F-Stigma, G-Anther
B) A-Sepal, B-Ovary, C-Petal, D-Filament, E-Anther, F-Stigma, G-Style
C) A-Ovary, B-Sepal, C-Filament, D-Petal, E-Anther, F-Stigma, G-Style
D) A-Petal, B-Anther, C-Stigma, D-Style, E-Filament F-Sepal, G-Ovary
3. A lake with an inflow of domestic sewage rich in organic waste may result in:
A) drying of the lake very soon due to algal bloom.
B) an increased production of fish due to lot of nutrients.
C) death of fish due to lack of oxygen.
D) increased population of aquatic food web organisation.
4. Which technique is used to detect AIDS?
a. Northern blot and ELISA
b. Immunoblot and ELISA
c. Western blot and ELISA
d. Southern blot and ELISA
5.
ANS B
6. Which of the following is not evident that the pattern of cleavage is determined by factors in
the egg cytoplasm rather than by genes of zygote
A) Cleavage is prevented by injection of a protein synthesis inhibitor
B) Cleavage is not affected by injection of inhibitors of RNA synthesis into the zygote
C) Interspecific hybrid zygotes go through normal cleavag but die at the beginning of
gastrulation
D) The direction of the first division of cleavage in the snail Cepaea is determined by the
mothers genotype
or
Identify the type of cell division A to D in the following
flowchart.
A) A-Meiosis-I, B-Mitosis, C-Mitosis, D-Meiosis
B) A-Meiosis-I, B-Meiosis-II, C-No division, D-Mitosis
C) A-Mitosis, B-No division, C-Meiosis-II, D-Meiosis-I
D) A-Mitosis, B-Mitosis, C-Meiosis-I, D-Meiosis-I
7.c DNA probes are copied from messenger RNA molecule with the help of
a. Restriction enzyme b. reverse transcriptase
c.DNA polymerase d. Adenosine deaminase
8. Select the correct statement regarding alkaline phosphatase.
(a) It is an enzyme that removes the phosphate group from the 5′ end of double stranded DNA.
(b) It is an enzyme that adds the phosphate group in the 5′ end of double stranded DNA.
(c) It is an enzyme that adds the phosphate group in the 3′ end of the double stranded DNA.
(d) It is an enzyme that removes the phosphate group from the 3′ end of double stranded DNA
9.In the hexaploid wheat, the haploid (n) and basic (X) numbers of chromosomes are
(a) n = 21 and X = 21 (b) n = 21 and X =14 (c) n = 21 and X = 7 (d) n = 7 and X =21
10. Select the incorrect statement regarding chemical fertilisers.
(a) They are easily soluble in water and are quickly absorbed by the plants.
(b) They can be applied to standing crops and are required in small quantities as compared to
manures.
(c) They adversely affect the useful microbes present in the soil.
(d) They improve physical properties of soil such as aeration, water holding capacity and
humus content.
11.
Identify A to D in the following diagram.
A) A - Filament (stalk), B - Pollen sac, C - Pollen grain, D - Line of dehiscence
B) A - Filament (stalk), B - Pollen sac, C - Line of dehiscence, D - Pollen grain
C) A - Line of dehiscence, B - Filament (stalk), C - Pollen sac, D - Pollen grains
D) A - Filament (stalk), B - Line of dehiscence, C - Pollen sac, D - Pollen grains
12. Read the following statements and select the correct ones.
(i) Cry proteins are toxic to insects and act as insecticides.
(ii) There are 53 amino acids present in insulin.
(iii) Bt-cotton was the first transgenic crop approved by commercial cultivation in India.
(iv) Brazzein is a high calorie-sweetner.
(a) (i) and (iii)
(b) (ii) and (iii)
(c) (ii) and (iv)
(d) (iii) and (iv)
13.
Given below diagram refers to the TS of testis showing few seminiferous tubules.
A, B, C and D in the above figure represent.
A) A-Sertoli cells, B-Secondaryspermatocyte, C-lnterstitial cells, D-Sperms
B) A-lnterstitial cells, B-Spermatogonia, C-Sertoli cells, D-Sperms
C) A-Sertoli cells, B-Spermatozoa, C-lnterstitial cells, D-Sperms
D) A-Sertoli cells, B-Spermatogonia, C-lnterstitial cells, D-Sperms
14.What is correct about a test tube baby?
(a) Fertilization in female’s genital tract and growth in test tube.
(b) Rearing of premature born baby in an incubator.
(c) Fertilization outside and gestation inside mother’s womb.
(d) Both fertilization and development are done outside the female genital tract.
15. Test tube babies are produced by
A) Fertilising the egg removed from the body of the female with the husband's sperm outside in vitro
culture. The zygote is transferred back
B) External fertilisation and development in vitro culture till 32 cells stage before putting the embryo
back into mother's uterus
C) Complete development of a baby in vitro
D) Development upto 32 cells stage and transplanting embryo in the uterus of a surrogate mother
16.Match the following columns.
Column I (Female reproductive Column II (Related to)
parts)
A Ovaries 1 Fertilisation
B Oviduct 2 Ovulation
C Uterus 3 Pregnancy
D Cervix 4 Childbirth
Codes
A) A-2 B-1 C-3 D-4
B) A-1 B-2 C-3 D-4
C) A-4 B-3 C-1 D-2
D) A-2 B-3 C-4 D-1
SECTION –B
17. With a neat, labelled diagram, describe the parts of a typical angiosperm ovule.
Ans:
A typical angiospermic ovule is a small structure which is formed in the ovary. Ovule first develops
as a projection on the placenta and composed of multilayered cellular tissue called the nucellus. The
hypodermal cell of die nucellus enlarges and transformed into megaspore mother cell. This cell
undergoes meiosis to produce four haploid cells only one of which develops & forms embryo sac
(female
18. Write the functions of
(i) cry IAc gene
(ii) RNA interference (RNAi) (Outside Delhi 2015C)
Answer:
(i) cry IAc codes for toxic insecticidal protein as inactive protoxins in Bacillus thuringiensis. This toxin kills
the cotton bollworm.
(ii) RNA interference is associated with silencing of specific ntRNA and is a method of cellular defence
in eukaryotes.
19.a. Mention the number of cells in the following stages.
Embryonic Stage Number of Cells
Zygote (i)
Morula (ii)
Blastocyst (iii)
Answer:
(i) 1 (ii) 16 (iii) 64
b.Name the hormones produced only during pregnancy in human female. Mention their source
organs.
Answer:
The hormones produced only during pregnancy in human female are human Chorionic and
placenta Gonadotropin (hCG), human Placental Lactogen (hPL) and relaxin.
The source of hCG and hPL is placenta and that of relaxin is ovary and placenta
20. A bilobed, dithecous anther has 100 microspore mother cells per microsporangium. How
many male gametophytes this anther can produce?
Answer:
An anther is a four-sided (tetragonal) structure consisting of four microsporangia.
Each microsporangium has 100 microspore
mother cells, so total number of microspore
mother cells in anther = 4 × 100 = 400
microspore mother cells. Meiosis in each microspore mother cell produces 4 male gametes, so
400 cells will produce = 4 × 400 = 1600 male gametes.
21. a. State what happens when an alien gene is ligated at Pvu I and Sal I site of pBR322
plasmid.
Answer:
An alien gene ligated at Pvu I site of pBR322 plasmid cause the transformant cell to loose the
ampicillin-resistance as ampR gene becomes non-functional. Thus, the recombinant does not
grow in the presence of ampicillin.
When an alien gene is ligated at Sal I site of tetracycline resistance gene in the vector pBR322,
the recombinant plasmid lose its tetracycline resistance.
b. Observe the given sequence of nitrogenous bases on a DNA fragment and answer the
following question
5 ́ - CAGAATTCTTA - 3 ́
3 ́ - GTCTTAAGAAT - 5 ́
(i) Name a restriction enzyme that can recognize this DNA sequence.
Ans: EcoRI is the name of a restriction enzyme that helps in the recognition of various
sequences of DNA.
(ii) Write the sequence after digestion.
(iii) Why are the ends generated after digestion called sticky ends?
Ans: The ends that are obtained after the digestion of the DNA sequences are called the sticky
ends because they result in the formation of hydrogen bonds with their complementary cut
parts.
SECTION –C
22. a. Removal of gonads cannot be considered as a contraceptive option. Why?
Ans: Removal of gonads or its parts is a surgical method, of sterilization. Vasectomy and tubectomy
are carried out in males and females respectively. It will lead to infertility & both male and female
will be dependent on hormones in their remaining life to regulate functioning of reproductive
organs. These are very effective but their irreversibility is very poor, so they are not good options
for contraception.
b.Define spermiogenesis and spermiation.
Ans: Spermiogenesis is the process of transformation of spermatids into mature flagellated
spermatozoa (sperms).Spermiation is the process of release of mature spermatozoa. In this
spermatozoa are shed into the lumen of seminiferous tubule for transport.
c. Mention two strategies evolved to prevent self-pollination in flowers.
Ans: Continued self-pollination decreases the vigour and vitality of a particular race. Thus,
flowering plants have developed many devices to discourage self-pollination and to encourage
cross-pollination.
Dichogamy and self-sterility are.two most common devices that ensure cross-pollination.
Dichogamy – Maturation of anther and stigma at different times in a bisexual flower prevent self-
pollination.
Self-sterility (or self-incompatibility) – Due to the presence of self-sterile gene in some flowers,
pollen grains do not germinate on the stigma of that flowers. e.g.,- tobacco, potato.
23. a.Why do the toxic insecticidal proteins secreted by Bacillus thuringiensis kill the insect and not
the bacteria itself?
Answer:
Bt toxin does not kill bacteria because in bacteria it exists in inactive state.
When Bt toxin is ingested by an insect, it gets converted into its active form due to the alkaline pH of the
gut.
The activated toxin binds to the surface of the epithelial cells of the midgut and creates pores. Water
enters through these pores and causes swelling and lysis of cells in insect body
b.How does dsRNA gain entry into eukaryotic cell to cause RNA interference?
Answer:
dsRNA gains entry into eukaryotic cell either through
infection by virus having RNA genome.
mobile genetic elements (transposons) that replicate via an RNA intermediate.
24. How are non-medicated IUDS different from hormone-releasing devices? Give
examples.
Ans. The difference between non-medicated IUDS and hormone-releasing devices is
given below.
Non-medicated IUDS Hormone Releasing IUDS
These types of IUDSs increase the These types of devices make the uterus and
phagocytosis of sperms within the cervix unsuitable for sperm by releasing
uterus, and the copper ions released hormones. Thus, they prevent the
suppress the motility and fertilising implantation process and act as
capacity of sperm. contraceptives.
Examples: Lippes Loop, Cu-T, Multiload Examples: Progestasert, LNG 20, etc.
375, etc.
25. The bacterium Bacillus thuringiensis produces a toxic protein called "cry protein". That protein is
lethal to certain insects, but not to bacteria.
Why does not this toxin kill bacteria?
After consuming this protein, what type of changes occur in the gut of insects?
How did humans use this protein for their benefit?
Ans.
a.Protoxin is produced in an inactive form.
b.This protoxin, in the presence of alkaline pH in the intestine of insects. The toxin binds to the surface
of the midgut of the insect that induces pore formation, swelling, and cytolysis, eventually leading to
death.
c.Isolation of specific Bt toxin genes from Bacillus thuringiensis and its integration into several crops
such as cotton and corn that are pest-resistant to specific insects.
26. a.What are chasmogamous flowers? Can cross-pollination occur in cleistogamous flowers? Give
reasons for your answer
Ans: Chasmogamous flowers are those flowers which are open with exposed anther and stigma.
Cleistogamous flowers are those flowers which do not open at all. In these flowers, the anthers and
stigma lie close to each other, when anthers dehisce in the flower buds, the pollen grains come in the
contact with stigma to effect pollination. So these flowers are invariably self-pollinated as the flowers
remain closed and there is no chance of cross pollen landing on the stigma. Pollination and seed setting
are assured even in the absence of pollinators
b. Amniocentesis for sex determination is banned? in our country. Is this ban necessary? Comment
Ans: Since Amniocentesis is misused to find out the sex of the foetus leading to female foeticides, it is
necessary. It is the prenatal diagnostic
technique, that helps to find out chromosomal (genetic) disorders, metabolic disorders of the foetus; in
extreme cases where the foetus is found to be suffering from an incurable disorder Medical Termination
of Pregnancy (MTP) is banned. The solution to the problem is not ‘ passing more laws, such as banning
sex determination ultrasounds but raising the social & economic status of women,
27. a.ß-galactosides enzyme is considered a better selectable marker. Justify the statement.
Answer:
Coding sequence of p-galactosidase is a better maker, as the recombinants and non-
recombinants are differentiated on the basis of their ability to produce colour in the presence of
a chromogenic substrate, while the selection of recombinants due to inactivation of antibiotic
resistant gene is a tedieus and time taking process to grow them simultaneously on two
antibiotics containing media.
b.Distinguish between the roles of flocks and anaerobic sludge digesters in sewage treatments.
Answer:
In sewage treatment, floes consume major part of the organic matter, converting it into microbial
biomass and releasing lot of minerals.
It reduces the BOD of sewage, while in anaerobic sludge digesters, many anaerobic bacteria
are present, which digest the organic mass. During this digestion, methane, CO 2 etc. are
produced.
28. With a neat diagram explain the 7-celled, 8- nucleate nature of the female gametophyte.
Ans:
Embryo sac (or female gametophyte) is formed by three successive mitotic divisions that take place
in the nucleus of megaspore.
The nucleus of the functional megaspore divides meiotically to form two nuclei which move to the
opposite poles, forming the 2-nucleate embryo sac. Two more sequential mitotic nuclear divisions
result in the formation of the 4-nucleate and later the 8-nucleate stages of the embryo sac. After the
8-nucleate stage, cell walls are laid down leading to the organisation of the typical female
gametophyte or embryo sac. Six of the eight nuclei are grouped together at micropylar and chalazal
end and form the egg apparatus and antipodals respectively. The large central cell left over with
two polar nuclei. Thus, a typical female gametophyte consists of 7 cells with 8 nucleus.
SECTION –D
Case Study Questions
The primary sex organs – the testis in the males and the ovaries in the females–produce gametes, i.e,
sperms and ovum, respectively, by the process called gametogenesis. In testis, the immature male germ
cells (spermatogonia) produce sperms by spermatogenesis that begins at puberty. The spermatogonia
(sing. spermatogonium) present on the inside wall of seminiferous tubules multiply by mitotic division
and increase in numbers.
I.Read the following
i)Each seminiferous tubule consists of two types of cells.
ii)Male germ cells are also called spermatogonia.
iii)Male germ cells undergo reduction division.
The correct combination
a)Only i & ii b)Only ii & iii c)i, ii, iii d)Only i & iii
II. In spermatogenesis. The phase of maturation involves…
a)Growth of spermatogonia into spermatocytes
b)Formation of spermatogonia from gonocytes through mitosis
c)Formation of spermatids from primary spermatocytes through meiosis
d)Formation of oogonia from spermatocytes through meiosis
III.Which is the correct sequence in Spermatogenesis?
a)Spermatogonia - Spermatids - Secondary spermatocytes - primary spermatocytes - sperms
b)Spermatogonia - Spermatids - primary spermatocytes - Secondary spermatocytes - sperms
c)primary spermatocytes - Secondary spermatocytes - Spermatids - Spermatogonia - sperms
d)Spermatogonia - primary spermatocytes - Secondary spermatocytes - Spermatids - sperms
IV. In humans, at the end of the first meiotic division, the male germ cells differentiate into the
a)Spermatids b)Spermatogonia c)Primary spermatocytes d)Secondary spermatocytes
V.Match the following
List – A List - B
A) Spermatogonia I) Sperms
B) Primary spermatocytes II) Production of sperms
C) Spermatocytes III) Meiosis
D) Spermiogenesis IV) Mitosis
A B C D
a) IV III I II
b) IV I II III
c) I II III IV
d) II III I IV
ans .(I) - c, (II) - c, (III) - d, (IV) - d, (V) - a
30.Read the following and answer any four questions from (i) to (v) given below:
Cross pollination is the transfer-of pollen grains from the anther of a one flower to the stigma of a
genetically different flower. It is performed with the help of an external agency which may be
abiotic (e.g., wind, water) or biotic (e.g., insects, birds, bats, snails). The diagram shows the carpel of
an insect pollinated flower.
(i) What is the most likely reason for non germination of pollen grain Z?
(a) Pollen grains X and Y were brought to the stigma earlier, therefore, their germination
inhibited the germination of pollen grain Z.
(b) Pollen grain Z was brought to the flower by wind, while pollen grains X and Y were
broughtto the flower by insect
(c) Pollen grain Z lacks protrusions that allow it to adhere properly onto the stigma surface
(d) Pollen grain Z comes from a flower of an incompatible species
(ii) Which of the following best describes the function of the pollen tube?
(a) It acts as a conduit to transport male gametes from the anther to the ovule
(b) It acts as a conduit to transport male gametes from the stigma to the ovule.
(c) It contains key nutrients that serve to nourish the newly-formed zygote
(d) It digests the tissues of the stigma, style and ovary.
(iii) Pollination of a flower in which the pollen is carried by an insect is called
(a) anemophily (b) ornithophily (c) entomophily (d) malacophily.
(iv) Refer to the given characteristics of some flowers:
A. The stamens hang out of the flower, B. The pollen grains C. The flower has D. The flower petals are
exposing the anthers to the wind. are tiny and light a sweet scent. brightly coloured.
(v)How many of the above characteristics are of insect-pollinated flower?
(a) One (b) Two (c) Three (d) Four
(vi) Pollenkitt is generally found in
(a) anemophilous flowers (b) entomophilous flowers (c) ornithophilous flowers (d) malacophilous flowers.
ANS DBCBB
SECTION –E
31. a) Explain the development of an embryo in a dicotyledonous plant with neatly labeled diagrams.
Ans: The embryo develops at the micropylar end where the zygote is located. The zygote begins
developing after the particular part of the endosperm is developed to ensure nutrition to the embryo.
The zygote breaks mitotically to develop several stages including pro- embryo, globular, heart-shaped,
and eventually the developed embryo.
.
b) (i) Draw a diagram of an enlarged view of TS of one microsporangium of an angiosperm
and label the following parts
(a) Tapetum
(b) Middle layers
(c) Endothecium
(d) Microspore mother cell
(ii) Mention the characteristic features and function of tapetum.
(iii) Explain the following giving reasons
(a) Pollen grains are well-preserved as fossils.
(b) Pollen tablets are in use of people these days.
Answer:
(i) For diagram. Refer
(ii) Tapetum is the inner nourishing layer of microsporangial wall. The cells of tapetum have
dense cytoplasm and more than one nucleus. These cells nourish the developing pollen grains.
(iii) (a) The outer exine layer of pollen grain is highly resistant because of sporopollenin. It is an
organic material which can withstand harsh conditions, action of alkalis and acids. No enzyme
can degrade sporopollenin. Thus, pollen grains are well-preserved as fossils.
(b) Pollen grains are rich in nutrients. So, used by people as health tablets or food supplements
32. (a) Mention the function of rop.
Ans: The rop is responsible for the coding of the proteins that are involved in the replication of
plasmids.
(b) What will be the selectable marker for this recombinant plasmid and why?
Ans: The selectable marker for this recombinant plasmid will be the ampicillin resistance gene.
They after placing them on an ampicillin-containing medium will undergo the process of plating
that will help in the differentiation between the trAns.formants from non-trAns.formants.
(c) Explain transformation.
Ans: Transformation is the process of transferring DNA from one cell and then placing them into
the other cell which will result in the formation of the recombinant cell consisting of the
properties of both the cells.
d. Describe the various steps involved in Recombinant DNA technology with the help of a
well labeled. Diagram?
Ans: The steps involved in the recombinant DNA are:
i) Identification of DNA with Desirable Genes: The addition of chilled ethanol will result in
obtaining the purified DNA while by using various other appropriate techniques the other
molecules in the target cell can also be removed.
ii) Cutting the DNA at a Specific Location: The source and vector DNAS after being cut will
be introduced together having a gene of interest and specific restriction site and will be joined
together with the help of an enzyme called ligase.
iii) Insertion of Recombinant DNA into Host Cell: The bacterial cell is first treated with the
specific concentration of divalent cation e.g., Ca2+ so that they can be competent enough to
take up the DNA in the plasmid. The calcium ions increase the efficiency of DNA to enter into a
bacterium through pores in its cell wall. It is a vector-less method.
iv) Selection & Screening: The selectable marker for this recombinant plasmid will be the
ampicillin resistance gene. They after placing them on an ampicillin-containing medium will
undergo the process of plating that will help in the differentiation between the trAns.formants
from non-trAns.formants.
v) Obtaining the Foreign Gene product: The gene of interest after its cloning along with the
presence of optimum growth conditions will result in the expression of target proteins which then
needs to be produced on a large scale.
OR
Explain the different phases of menstrual cycle and correlate the phases with the different levels
of pituitary hormones in a human female.
33. Suggest some methods to assist infertile couples to have children.
Ans: ART (Assisted Reproductive Technologies) is a term that describes several different methods
used to help infertile couples. ART involves removing eggs from a woman’s body, mixing them with
sperm in the laboratory and putting the embryos bath into a woman’s body.
Success rates vary depending on many factors.Something that affects the success rate of ART
includes age of the partners, reason for infertility,type of ART, if the egg is fresh or frozen. Various
methods are now available to help such couples are — in vitro fertilization, gamete intra fallopian
transfer, intracytoplasmic sperm injection & artificial insemination.
(i) In vitro fertilization – Patient’s egg & her partner’s sperm are collected & mixed together in a
laboratory to achieve fertilization outside the body. The embryo produced may then be transferred
into the female patient. It is commonly knownas test tube baby programme.
(ii) Gamete Intra Fallopian Transfer (GIFT) – A procedure in which eggs are retrieved from a
woman, mixed with sperm & immediately replaced in one or other of the women’s fallopian tubes
so that they fertilize inside the body (invivo).
(iii) Intra Cytoplasmic Sperm Injection (ICSI)– In this method, sperm & eggs are retrieved from
both the parents. A single sperm is injected directly into an egg, then the fertilized egg is implanted
into the woman’s uterus.
(iv)Artificial insemination – In this technique, the semen is collected either from husband or a
healthy donor & is artificially introduced either into the vagina or into the uterus of the female (IUI-
Intra uterine insemination).
