NCERT Solutions – Chapter 8 Heredity and Inheritance

Subject: Science | Class: 10 | Chapter 8

Introduction

Heredity is the process by which traits are passed from parents to offspring. Gregor Mendel’s experiments on pea plants laid the foundation for modern genetics. This chapter explains how genes control the inheritance of characteristics such as height, flower color, and other traits in living organisms.

Exercise Solutions

1. A Mendelian experiment consisted of breeding tall pea plants bearing violet flowers with short pea plants bearing white flowers. The progeny all bore violet flowers, but almost half of them were short. This suggests that the genetic makeup of the tall parent can be depicted as:

Answer: ✅ (d) TtWw

Explanation:

The tall (T) trait is dominant over short (t).
The violet flower color (W) is dominant over white (w).
Since all offspring have violet flowers, the tall parent must have at least one dominant allele W.
Half of the offspring being short indicates that the tall parent was heterozygous for height (Tt).
Thus, the genotype of the tall parent is TtWw.

2. A study found that children with light-colored eyes are likely to have parents with light-colored eyes. On this basis, can we say anything about whether the light eye color trait is dominant or recessive? Why or why not?

Answer:
No, we cannot conclude whether the light eye color trait is dominant or recessive based solely on this observation.
Reason:
The study shows a correlation but does not provide information about the genetic makeup (genotype) of the parents or the mode of inheritance. Environmental factors or incomplete dominance could also influence eye color. Controlled breeding experiments are required to confirm dominance or recessiveness.

3. Outline a project which aims to find the dominant coat color in dogs.

Answer:
Project: Determining the Dominant Coat Color in Dogs

Steps:

Select two breeds of dogs with different coat colors (e.g., black and brown).
Cross a pure black-coated dog with a pure brown-coated dog.
Observe the coat color of the F₁ generation (offspring).
If all F₁ pups have the same color (e.g., black), that color is dominant.
Cross two F₁ offspring to produce an F₂ generation.
If the F₂ generation shows a ratio of 3:1 (dominant:recessive), it confirms Mendelian inheritance.

4. How is the equal genetic contribution of male and female parents ensured in the progeny?

Answer:
During sexual reproduction:

The male parent contributes sperm (which carries 23 chromosomes) and
The female parent contributes an egg (which also carries 23 chromosomes).
When fertilization occurs, the zygote receives 23 chromosomes from each parent, forming a complete set of 46 chromosomes.
Thus, equal genetic contribution is ensured from both parents in the offspring.

Conclusion

Mendel’s experiments on pea plants helped establish the laws of inheritance, explaining how traits pass from parents to offspring. Understanding heredity allows us to predict characteristics, study genetic disorders, and appreciate the role of genes in evolution and biodiversity.