CBSE Class 12 Biology – Principles of Inheritance and Variation

Chapter Overview

This chapter introduces genetics—the science of heredity and variation. It explores Mendel’s laws, chromosomal basis of inheritance, deviations like incomplete dominance and co-dominance, linkage, sex determination, mutation, and genetic disorders.

Important Keywords

• Heredity: Passing traits from parents to offspring.
• Variation: Differences among individuals of a species caused by genetic recombination, mutation, environment. :contentReference[oaicite:1]{index=1}
• Gene: Unit of inheritance located on chromosomes.
• Allele: Alternative forms of a gene. e.g., T or t. :contentReference[oaicite:2]{index=2}
• Dominant/Recessive: Dominant allele masks the recessive in heterozygote. :contentReference[oaicite:3]{index=3}
• Genotype/Phenotype: Genetic makeup vs observable traits. :contentReference[oaicite:4]{index=4}
• Mutation: Permanent change in DNA sequence contributing to variation. :contentReference[oaicite:5]{index=5}
• Linkage: Genes on the same chromosome inherited together. :contentReference[oaicite:6]{index=6}