Genetics – Some Basic Fundamentals

Appeared in 10 of the 11 available papers.

Examined in

10 of 11 papers

Appears almost every year — treat as core

Typically worth

6.2 marks

Average per paper it appears in · 62 marks in total

Usual form

Short answer

27% of this chapter's 62 questions

Needs a diagram

5 questions carry a figure — practise drawing them

Question-type distribution

Short answer17
MCQ14
Definition13
Reasoning10
Biological term5
Odd one out2
Analogy1

Most frequent topics

Mutation 4Law of Dominance 3Dihybrid cross — F1 generation 3Gametes of a dihybrid 3Dihybrid F2 phenotypic ratio 3Genetic disorders vs infectious diseases 2Allele 2Recessive allele 2

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Showing 25 of 62 matching questions (62 marks).

25 questions

Select the correct answers to the questions from the given options. (Do not copy the questions, write the correct answer only.)

1(i)2026

MCQEasy1 mark

Four friends P, Q, R, and S were discussing the examples of genetic disorders. The examples they quoted were as follows: P. Colour blindness and Malaria Q. Albinism and Cholera R. Haemophilia and Colour blindness S. Haemophilia and Albinism Who gave the correct examples?

(a)P and Q
(b)R and S
(c)P and R
(d)Q and S

1(viii)2026

MCQHard1 mark

A family has a history of colour blindness. During genetic testing it was found that the mother is a carrier of colour blindness (XᶜX) and the father has normal vision (XY). What is the probability of their sons being colour blind?

(a)25%
(b)50%
(c)75%
(d)0%

1(v)2025

MCQModerate1 mark

A scientist wanted to conduct a genetic experiment on mice. He cut the tails of all the mice and made them reproduce. What will be the phenotype of the offsprings?

(a)All the offsprings will be tailless.
(b)There will be a mix of tailed and tailless offsprings.
(c)All the offsprings will have tails.
(d)Tail of the offsprings cannot be predicted.

1(viii)2025

MCQHard1 mark

Ajay and Vijay are siblings. Ajay can roll his tongue while Vijay cannot. What is the genotype of their parents?

(a)Both the parents are homozygous dominant.
(b)Both the parents are homozygous recessive.
(c)One parent is homozygous dominant, and the other is homozygous recessive.
(d)Both the parents are heterozygous dominant.

7(i)2025

DefinitionModerate1 mark

Define the term Allele.

8(v)

A farmer cultivates a unique species of tomato plants. The two traits selected for breeding were the colour of the fruits and the height of the plants. The farmer initially crosses a homozygous tall plant bearing red fruits (TTRR) with a dwarf plant bearing yellow fruits (ttrr), and the genotype of all the offsprings of the F1 generation was TtRr. Next, he crosses two F1 generation plants (TtRr).

8(v)(a)2025

ReasoningModerate1 mark

Explain the phenotype of the offsprings of the F1 generation obtained from the initial cross.

8(v)(b)2025

Short answerModerate1 mark

Mention the phenotypic ratio of the F2 generation offsprings.

DefinitionModerate1 mark

State Mendel’s Law of Independent Assortment.

Select the correct answers to the questions from the given options. (Do not copy the questions, write the correct answer only.)

1(vi)2024

MCQModerate1 mark

A zygote which has Y chromosome inherited from the father will develop into a:

(a)Will depend on the chromosome inherited from the mother
(b)Girl
(c)Either boy or a girl
(d)Boy

1(x)2024

MCQEasy1 mark

Four friends P, Q, R and S were discussing the examples of genetic disorders. The examples they quoted were as follows: P. Colour blindness and malaria Q. Albinism and cholera R. Haemophilia and colour blindness S. Haemophilia and albinism Who gave the correct examples?

(a)P and Q
(b)R and S
(c)P and R
(d)Q and S

5(v)

Given below is a schematic representation of the inheritance of the shape of seeds of garden pea. Answer the questions that follow.

5(v)(a)2024

Short answerModerate1 mark

Which is the dominant and recessive allele of the trait?

5(v)(b)2024

Short answerModerate1 mark

What does the ratio 3 : 1 in the F2 generation represent?

DefinitionModerate1 mark

State Mendel’s Law of Dominance.

Select the correct answer to the questions from the given options. (Do not copy the questions, write the correct answer only.)

1(i)2023

MCQModerate1 mark

The sex chromosome in a human ovum is:

(a)X chromosome
(b)Y chromosome
(c)Both X and Y chromosome
(d)Either X or Y chromosome

2(i)

Name the following:

2(i)(b)2023

Biological termModerate1 mark

A genetic disorder in which the blood does not clot.

4(iv)2023

DefinitionModerate2 marks

State Mendel’s Law of Segregation.

8(i)2023

DefinitionModerate1 mark

Define the term Mutation.

8(ii)2023

ReasoningHard2 marks

A pure breeding red flower variety of pea plant (RR) is crossed with a pure breeding white flower variety of pea plant (rr). Draw a Punnett square to find out the Phenotypic and Genotypic ratios of the progeny belonging to the F2 generation.

Name the following by choosing the correct option:

1(iv)2021

MCQModerate1 mark

The type of gene, which in presence of a contrasting allele is not expressed:

(a)Homozygous
(b)Heterozygous
(c)Dominant
(d)Recessive

Complete the following statements by choosing the appropriate option for each blank:

2(ii)2021

MCQModerate1 mark

The genotype of a person who cannot roll his tongue is __________.

(a)Rr
(b)RR
(c)rr
(d)RRr

2(v)2021

MCQEasy1 mark

The basic units of heredity are __________

(a)Chromosomes
(b)Chromatids
(c)Genes
(d)Centrosome

Choose the correct answer from each of the four options given below:

3(iii)2021

MCQModerate1 mark

A homozygous pea plant having purple flowers is crossed with a homozygous pea plant bearing white flowers. The phenotypic ratio of the offspring obtained in F2 generation is:

(a)2:1
(b)1:1
(c)1:2:1
(d)3:1

Explain the following terms:

4(ii)2021

MCQModerate1 mark

Law of Dominance:

(a)Out of a pair of contrasting alleles present together, only the recessive allele is able to express itself while the dominant remains suppressed
(b)Out of a pair of contrasting alleles present together, only the dominant allele is able to express itself while the recessive remains suppressed
(c)Out of a pair of contrasting alleles present together, both dominant and recessive cannot express themselves
(d)Out of a pair of contrasting alleles present together, both dominant and recessive can express themselves

4(iii)2021

MCQModerate1 mark

Mutation:

(a)It is a sudden change in one or more genes in an organism’s cells which is heritable
(b)It is a change in the number of centrosomes in an organism’s cell which is heritable
(c)It is a change in the structure of cell membrane in an organism’s cells which is heritable
(d)It is a change in the shape of cells which is heritable

1(b)(i)2020

DefinitionModerate1 mark

Allele