PROBLEM BASED QUESTIONS: HEREDITY
1. Mendel’s experiment to study inheritance in the pea plant (Pisum sativum) is shown in the
following diagram. Study the diagram carefully and complete the empty boxes by filling
them properly.
2. Ranjeet has 3 daughters. His wife is pregnant again. She was asked to go for sonography of the
‘X’ and remove foetus if it is found to be female..
(i) Who is responsible for the sex of the ‘X ‘children? Why?
(ii) Is removing female foetus correct measure?
(iii) Which sex chromosome of Ranjeet was not used in case of birth of his 3 daughters?
(iv) Why is prenatal sex determination banned?
(v) How can you counsel Ranjeet?
3. You are supplied with two sets of seeds of pea plants. One set is yellow and round seeds with
gene constitution YYRr and other set is green and round seeds with gene constitution yyRR. These
plants are cultivated, where Pea plant is self-pollinated. Which offsprings do you expect? Show
with chart.
4. You observed trait of earlobe whether they are free or attached in four different couples, along
with their children.
(i) Couple has all the children with free earlobe even though the mother has attached earlobe. What
do you think about father’s earlobe?
(ii) Couple has children with 1 : 1 ratio for free and attached earlobe. What do you think about the
father-mother for this trait?
(iii) In a couple, both father and mother have attached earlobe. What do you think about their
children?
(iv) A couple has four children, out of which three have free earlobe and one has attached earlobe.
What do you think about their parents?
OR
Attached ear lobe in human is an inherited condition. The allele for attached earlobes is recessive.
What are the chances of parents, both having free earlobes, to have a child with attached earlobes?
5. The farmer crosses two heterozygous green seeded plants and obtain 100 plants in the F1
generation. What would be the number of green and yellow seeds respectively in the F1
generation?
What should be the genotype of the parent plants to give green and yellow seeds in equal
proportions?
6. Consider a pea plant that is recessive for plants for plant height. Its genotype is tt and phenotype
is dwarf.
(a) Assuming that the gene for plant height obeys the Mendelian laws of inheritance, indicate the
genotype and phenotype of ALL the possible parent pairs that could have dwarf offsprings.
(b) Using any of the parent pairs mentioned by you in (a), perform a cross to show the genotypes
of the offspring that might arise in the next generation.
7. If 1600 plants were obtained in F2 progeny with the number of the plants having traits:
(a) Tall and round seeds (b) Short with wrinkled seeds (c) Short and round seeds
Write the conclusion of the above expression.
8. Two human beings who can both roll their tongues produced 11 children. 3 of these children not
roll their tongues and 8 children could roll their tongues.
(a) Which trait (Rolling or non-rolling) is controlled by the recessive allele?
(b) State all the possible genotypes of the F1 generation of the cross.
(c) Show the inheritance of the tongue rolling in humans in the given example using a suitable
cross. What percentage of offspring will show the same genotype as the parents?
(d) If one of the parent could not roll their tongue, with the help of a cross, calculate the ratio of
tongue-roller to non-tongue roller in the offsprings.
9. A person first crossed pure-breed pea plants having round yellow seeds with pure breed pea plant
having wrinkle green seeds and found that only A-B type of seeds was produced in the F1
generation. When F1 generation pea plants having A-B type of seeds were cross breed by selfpollination, then in addition to the original round yellow and wrinkle green seeds, two varieties AD and C-D types of seeds were also obtained.
(i) What is A-B type of seeds?
(ii) State whether A and B types of seeds are dominant traits or recessive traits.
(iii) What is A-D type of seeds?
(iv) What is C-B type of seeds?
(v) Out of A-B and A-D type of seeds, which one will be produced in (a) minimum number and (b)
maximum number in the F2 generation.
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