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NCERT Solutions Class 10 Science Chapter 8 Heredity: Questions, Answers and PDF

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eSaral Academic and Editorial Team

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Summary

These NCERT Solutions Class 10 Science Chapter 8 Heredity notes give short, correct answers to the in-text and exercise questions, a chapter summary of variation, Mendel’s experiments and sex determination, key terms, common mistakes and FAQs, with the full solutions in the free eSaral PDF.

NCERT Solutions Class 10 Science Chapter 8 Heredity: Mendel’s cross and sex determination

NCERT Solutions Class 10 Science Chapter 8 is about Heredity: how traits pass from parents to children, what Mendel’s pea-plant experiments showed, and how the sex of a child is decided. The chapter has 10 questions, 6 in-text questions and 4 exercise questions. In these NCERT Solutions Class 10 Science Chapter 8, you get the answers to check your work, a summary of the chapter, the key terms, the common mistakes, and the free eSaral PDF with the complete solutions.

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NCERT Solutions Class 10 Science Chapter 8 Heredity: Answers at a Glance

Question

What it asks

Short answer

In-text 1

Trait A in 10% and trait B in 60% of an asexually reproducing population: which arose earlier?

Trait B, because it has had time to spread to more individuals

In-text 2

How does variation help a species survive?

When the environment changes, some individuals with a suitable variation survive, so the species is not wiped out

In-text 3

How do Mendel’s experiments show dominant and recessive traits?

In the F1 generation only one trait shows (dominant), and the other trait comes back in about one-fourth of the F2 plants (recessive)

In-text 4

How do they show that traits are inherited independently?

In a dihybrid cross, the F2 generation has new combinations (round green and wrinkled yellow seeds) in a 9 : 3 : 3 : 1 ratio

In-text 5

Blood group A man and blood group O woman, daughter has group O: which trait is dominant?

The information is not enough: both A dominant and O dominant fit the data

In-text 6

How is the sex of a child decided in humans?

By the sperm: it carries X or Y, and every egg carries X

Exercise 1

Tall parent genotype when all F1 are violet and about half are short

(C) TtWW

Exercise 2

Can light eye colour be called dominant or recessive from light-eyed parents and children?

No, the data fits both

Exercise 3

Outline a project to find the dominant coat colour in dogs

Survey dogs, record the colours in a table, and test dominance by crossing

Exercise 4

How is equal genetic contribution of both parents ensured?

Each parent gives one set of chromosomes through a gamete, and the zygote gets half from each

The full working of these NCERT Solutions Class 10 Science Chapter 8 answers, with the project table, is in eSaral’s free PDF.

NCERT Solutions Class 10 Science Chapter 8 Topics

Section

Topic

8

Heredity

8.1

Accumulation of variation during reproduction

8.2

Heredity

8.2.1

Inherited traits

8.2.2

Rules for the inheritance of traits: Mendel’s contributions

8.2.3

How do these traits get expressed?

8.2.4

Sex determination

In the NCERT Solutions Class 10 Science Chapter 8, section 8.1 and section 8.2 are the two parts of the chapter.

8.1 Accumulation of variation during reproduction: when a cell copies its DNA, small errors occur, and these give rise to variations. Sexual reproduction mixes the DNA of two parents, so it creates much more variation than asexual reproduction. Variation helps a species survive when its surroundings change.

8.2 Heredity: heredity is the passing of traits from parents to offspring through genes. A gene is a part of DNA that carries the instructions for a trait. A change in the body cells during a lifetime (an acquired trait) does not change the DNA of the germ cells, so it is not inherited.

Key Points of Class 10 Science Chapter 8 Heredity

These are the points that the NCERT Solutions Class 10 Science Chapter 8 questions test most:

  • Mendel’s experiments: Mendel crossed pea plants with contrasting traits. When he crossed a tall plant with a short plant, all the F1 plants were tall. In F2, tall and short plants appeared in the ratio 3 : 1. So the tall trait is dominant and the short trait is recessive.
  • Independent inheritance: in a cross between plants with round yellow seeds and wrinkled green seeds, the F1 plants were all round and yellow. In F2, four types appeared in the ratio 9 : 3 : 3 : 1, which includes new combinations. So the two traits are inherited independently.
  • Genes in pairs: each trait is controlled by a pair of factors, one from each parent. When the two are different, the dominant one shows, and the recessive one shows only when both are recessive.
  • Genotype and phenotype: the genotype is the combination of genes (for example Tt), and the phenotype is the visible trait (for example tall).
  • Equal contribution: the child gets half of the chromosomes from the mother and half from the father, so both parents contribute almost equally.
  • Sex determination in humans: humans have 23 pairs of chromosomes, and one pair decides the sex. Females are XX and males are XY. All eggs carry X, and a sperm carries X or Y, so the sperm decides the sex of the child. The chance of a boy or a girl is 50% each.
  • Acquired traits: changes in the body cells during a lifetime are not passed to the next generation, because the DNA in the germ cells does not change.
  • DNA: DNA is the genetic material that carries the information of heredity.

Key Terms in NCERT Solutions Class 10 Science Chapter 8

Term

Meaning

Heredity

The passing of traits from parents to offspring

Variation

The differences among the individuals of a species

Trait

A visible feature, such as height or flower colour

Gene

A part of DNA that carries the instructions for a trait

Dominant trait

The trait that shows in the F1 generation

Recessive trait

The trait that is hidden in F1 and shows only when both factors are recessive

F1 and F2

The first and the second generation after the cross

Genotype

The combination of genes of an individual (for example Tt)

Phenotype

The visible trait of an individual (for example tall)

Gamete

A sex cell (egg or sperm) with half the number of chromosomes

Worked Example for NCERT Solutions Class 10 Science Chapter 8: A Monohybrid Cross

Cross two F1 plants with the genotype Tt (tall). Each plant makes two kinds of gametes, T and t.

 

T

t

T

TT (tall)

Tt (tall)

t

Tt (tall)

tt (short)

This is the type of cross that appears in the NCERT Solutions Class 10 Science Chapter 8 answers. The genotype ratio is TT : Tt : tt = 1 : 2 : 1, and the phenotype ratio is 3 tall : 1 short. This is the 3 : 1 ratio that Mendel found in F2, and it is the most asked result of this chapter.

Common Mistakes in NCERT Solutions Class 10 Science Chapter 8

Students often lose marks in the NCERT Solutions Class 10 Science Chapter 8 questions for these reasons:

Mistake

Correct approach

Writing that traits pass “from one parent to another”

Traits pass from parents to offspring

Mixing up genotype and phenotype

Genotype is the genes, phenotype is the visible trait

Saying that a recessive trait shows in a Tt plant

A recessive trait shows only when both factors are recessive (tt)

Saying that the mother decides the sex of the child

The sperm decides it, because it carries X or Y

Saying that acquired traits are inherited

Changes in body cells do not change the DNA of the germ cells

Giving only the final answer in a cross question

Write the parents, the gametes, F1, F2 and the ratio

💡 Tip from the eSaral Academic Team: For any cross question in NCERT Solutions Class 10 Science Chapter 8, write the parents’ genotypes, their gametes, a small table for the offspring, and then the genotype and the phenotype ratios. This habit gets full marks in Heredity answers even if one step goes wrong.

Reproduction in Chapter 7 is the base for NCERT Solutions Class 10 Science Chapter 8, so you can revise it with eSaral’s NCERT Solutions for Class 10 Science Chapter 7. All the chapters are listed on eSaral’s NCERT Solutions for Class 10 Science page.

Frequently Asked Questions

What is heredity in Class 10 Science?

Heredity is the passing of traits from parents to offspring through genes. It is why children look like their parents.

How many questions are there in NCERT Solutions Class 10 Science Chapter 8 Heredity?

There are 10 questions in Class 10 Science Chapter 8 Heredity: 6 in-text questions and 4 exercise questions. eSaral’s free PDF has the solution of all of them.

What is the answer to Exercise Question 1 of NCERT Solutions Class 10 Science Chapter 8?

The answer is (C) TtWW. All the progeny are violet, so the violet parent is WW, and about half of them are short, so the tall parent is Tt (a Tt × tt cross gives half tall and half short).

How do Mendel’s experiments show that traits are dominant or recessive?

In NCERT Solutions Class 10 Science Chapter 8, the answer is based on the monohybrid cross. When Mendel crossed a tall pea plant with a short one, all the F1 plants were tall, so only one trait showed. In F2, short plants appeared again in about one-fourth of the plants. The trait that shows in F1 is dominant, and the one that is hidden and returns in F2 is recessive.

How is the sex of a child determined in human beings?

Females have two X chromosomes (XX) and males have one X and one Y (XY). Every egg carries an X, and a sperm carries either X or Y. If an X sperm fertilises the egg, the child is a girl, and if a Y sperm does, the child is a boy.

Is the blood group information enough to say whether A or O is dominant?

No. If A is dominant, the father must be AO, and the daughter gets O from him and from her mother. If O is dominant, the father can be AA, the mother can carry both alleles, and the daughter then shows O as the dominant trait. Both cases fit the data, so it does not decide which is dominant.

Why are traits acquired during the lifetime of an individual not inherited?

An acquired trait is a change in the body cells, and it does not change the DNA in the germ cells (the egg and the sperm). Only a change in the germ cells can be passed to the next generation.

Is evolution part of Class 10 Science Chapter 8?

No. In the current NCERT book, Chapter 8 is Heredity, and it covers variation, Mendel’s experiments, expression of traits and sex determination. Questions on fossils and homologous organs belong to the older chapter “Heredity and Evolution”, so ignore them if your book is the current one.

Where can I find the full solutions of NCERT Solutions Class 10 Science Chapter 8?

The complete working of all the questions, including the dog coat colour project, is in eSaral’s free PDF for Class 10 Science Chapter 8 Heredity. This page gives the short answers, the key points and the common mistakes to go with it.

Is Heredity important for the Class 10 board exam?

Yes. Heredity is part of the Unit “World of Living” in the CBSE Class 10 Science syllabus, and questions are asked on Mendel’s cross, the 3 : 1 and 9 : 3 : 3 : 1 ratios, and sex determination. Practise the cross steps, and use the NCERT Solutions Class 10 Science Chapter 8 questions for the exact wording.

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