Chapter 8 — Heredity

Heredity is the reliable inheritance of traits from parents to offspring through genes. Gregor Johann Mendel's experiments on pea plants established the fundamental rules of inheritance, including dominant and recessive traits and independent assortment.

NCERT Class 10 Science Chapter 8 covers Heredity — the mechanism by which traits are transmitted across generations. It explains how variations accumulate during reproduction and how sexual reproduction maximises diversity. Mendel's experiments with pea plants revealed that traits are controlled by two copies of genes (now called alleles), with dominant traits expressed over recessive ones. The chapter also explains how genes are carried on chromosomes and how sex is genetically determined in humans through X and Y chromosomes, with the father's chromosome deciding the child's sex.

1. 01Variations arising during reproduction can be inherited, and natural selection favours variants better suited to their environment.
2. 02Mendel used pea plants with contrasting traits (tall/short, round/wrinkled seeds) to establish laws of inheritance across F1 and F2 generations.
3. 03In F1 crosses, only one parental trait (dominant) appears; in F2, the ratio of dominant to recessive is approximately 3:1.
4. 04Two traits (e.g., seed shape and seed colour) are inherited independently of each other, producing new combinations in offspring.
5. 05Genes are carried on chromosomes; each cell has two copies of each chromosome, one from each parent, while germ cells carry only one copy.
6. 06In humans, sex is determined by sex chromosomes — females are XX, males are XY; the father's X or Y chromosome determines the child's sex.