VELAMMAL BODHI CAMPUS –KOLAPAKKAM

UNIT VII
BIOLOGY –WORK SHEET
STD-XII

Q. Question Marks
No
Multiple Choice Question

Q.1 In mice, brown fur is dominant and white fur is recessive. A biologist crossed a 1
brown fur male with a white fur female and obtained two brown fur and two
white fur offspring. Which of the following statements is MOST likely to be true?
A. Both parents are heterozygous.
B. Only the male parent is homozygous.
C. Only the male parent is heterozygous.
D. Only the female parent is heterozygous.

Q.2 In which of the following process would genetic variation occur? 1

P) mutation in liver cells
Q) development of a zygote to an embryo
R) gene flow from one population to another
A. only P
B. only Q
C. only P and Q
D. only P and R

Free Response Question/ Subjective Question

Q.3 (a) What is the mode of inheritance of traits causing haemophilia? 3

(b) What would be the possibility of a female and male child having
haemophilia in the following scenarios?
(i) the mother is a unaffected and the father is affected
(ii) the mother is a carrier and the father is unaffected

Q.4 (a) State two points of difference between aneuploidy and polyploidy. 3
(b) Failure in which phase of cell division can cause the conditions mentioned in
(a)?
Q.5 In pea plants, inflated (A) and green (B) pods with round (C) seeds and the male 5
with constricted (a) and yellow (b) pods with wrinkled (c) seeds.
Mendel performed a cross to study the inheritance of these three traits. He
performed a cross between two parents that were heterozygous for all the
traits.
Identify the:
(a) Genotype of the gametes.
(b) Number of offspring in the F1 generation. Give a reason to support your
answer.
(c) Number of offspring who are homozygous for all traits. State their
phenotype.

Q.6 A colour-blind father will not have a colour-blind son. 2

State if the above statement is true and justify your answer if the mother is
homozygous for the:
(a) colour blind trait
(b) normal vision trait

Q.7 Rett syndrome is a rare X-linked dominant genetic neurological and 2

developmental disorder that affects the way the brain develops.
What would be the occurrence of the disease in their daughter and son, if:
(a) a normal male marries a female with Rett syndrome
(b) a normal female marries a male with Rett syndrome

Q.8 State TWO points of difference and TWO points of similarity 2

between Klinefelter's syndrome and Turner's syndrome.

Q.9 Using a Punnett square, determine the genotype of the parents if their child can 2
have any of the four blood groups.

Q.10 Duchenne muscular dystrophy is an X-linked recessive genetic disease that is 3

also caused by mutations in the DMD gene.
Predict the genotypic and phenotypic ratios of the possible offspring of a male
with muscular dystrophy and a female who is a carrier using suitable symbols
for the alleles in a Punnett grid.
Q.11 A gardener has been planting white flowers that grow on the terminal ends of 5
the plant in a garden for several months.
One day, a purple flower along the terminal end of the plant grows. The
gardener wants to know if these flowers would give rise only to purple terminal
flowers if pollinated. She knows that purple axial alleles are recessive over white
terminal ones.
(a) What are the possible genotypes of the new purple flower that sprouted?
(b) If she wants to use only one generation to determine its genotype, what
should she do?
(c) With the help of a Punnett grid/s, help her make inferences to arrive to the
conclusion she desires.

Q.12 Sickle cell anemia (allele a) is a disorder where the RBCs stretch out and become 3
thin as opposed to the round normal (allele A) RBCs. A person who is
homozygous for normal RBCs marries a person who is heterozygous for sickle
cell RBCs.
What is the probability of the off-springs to be homozygous for the sickle cell
trait?
Blood from one of the off-springs was checked and the microscopic image of its
RBCs is shown below.

What is the genotype of this individual?

(c) Based on the image shown, explain the type of dominance exhibited by
the sickle cell allele?
Q.13 Mia's family consists of her grandparents, brother, sister and parents. Her 5
parents are the only off-springs of her paternal and maternal grandparents. She
is the only one in her family who has thalassemia. Of her 4 grandparents, her
maternal grandmother had thalassemia.
Describe the method she can use to analyse the inheritance of thalassemia in
her family.
Draw an illustration to show the pattern of inheritance.
What is the mode of inheritance? Justify your answer.

Q.14 A roan cattle is an animal that has both red (R) and white (R') hair on its coat. 3
Consider that two cows - one pure line for white hair and one pure line for red
hair are crossed.
What would be the genotype and phenotype of the F1 and F2 generations?
What kind of dominance does the gene for hair colour exhibit? Give a reason to
support your answer.

Q.15 State THREE advantages of using Drosophila as the model organism for studying 3
genetics as compared to Mendel's pea plant.

Q.16 Given below is a pedigree chart for an autosomal dominant disorder 2

characterised by trait 'A'.

What evidence in the pedigree chart helps establish that the condition is caused
by a dominant allele?
What are the genotypes of the affected and unaffected individuals?
Q.17 Given below is the pedigree of a family for a trait. 3

Identify the mode of inheritance of the trait. Give a reason(s) to support your
answer.
Choose the correct answer to complete the following sentence:
Colour blindness is a sex-linked condition. However, a
(heterozygous/homozygous) (male/female) will always have normal
vision.

Q.18 Cystic fibrosis is a condition in which a defective cf gene (consider allele c) 3

produces faulty transport channels that causes mucus to build up in the ducts
of different organs leading to vitamin deficiency diseases, respiratory
infections and excessive loss of salt through sweat.
Given below is a pedigree chart for a family. The great-grandmother,
represented as I- 1, suffers from cystic fibrosis.

Identify the type of expression of the cystic fibrosis gene. Give a reason to
support your answer.
From the pedigree, deduce the pattern of inheritance exhibited by the gene.
Justify your answer.
Identify the genotypes of II-2 and III-2.
Q.19 Given below is the karyotype of an individual. 2

What are the characteristic reproductive and physical features of such an

individual?
What is the category of such disorders called? How is it caused?

Q.20 Which of the following occurs as a result of DNA replication being semi- 1
conservative?
A. Chromosome number becomes half in the gametes.
B. Each chromosome has half DNA and half RNA.
C. Parental characters are found in each chromosome.
D. Each new DNA strand has half the number of nucleotides compared to
the parent DNA strand"

Q.21 An organism has 6 X 109 bp in its DNA. Which of the following is likely to be 1
closest in height to the length of its DNA molecule?
- A wardrobe: 2 m
- A tall tree: 20 m
- An A4 sheet: 20 cm
- A eukaryotic nucleus: 10-10 m
A. A wardrobe
B. A tall tree
C. An A4 sheet
D. A eukaryotic nucleus
Q.22 Which of the following is true about the structure of DNA and RNA? 1
P) The nitrogenous base is devoid of an OH group in DNA.
Q) The nitrogenous base of RNA gains the OH group lost by DNA.
R) The pentose sugar in RNA combines with an extra OH group.
S) The pentose sugar in DNA loses an OH group to form deoxyribose.
A. only P
B. only S
C. only R and S
D. only P and Q

Q.23 Which of the following statement/s are correct example/s of the degenerate 1
feature of the genetic code?
UAA and UAG act as terminator codons.
CUA codes for leucine in bacteria as well as humans.
Valine is coded for by GUU and GUC.
A. only Q
B. only R
C. only P and Q
D. only P and R