Principles of Inheritance and Variation

Chapter 4 of Class 12 Biology — the genetics chapter. Covers Mendel's laws (dominance, segregation, independent assortment), deviations from Mendelism (incomplete dominance, codominance, multiple alleles, ABO blood groups), the Chromosomal Theory of Inheritance, linkage and recombination (Morgan's Drosophila work), polygenic inheritance, pleiotropy, sex determination across animal kingdoms (XY, XO, ZW, haplodiploid), sex-linked inheritance with pedigree analysis (haemophilia, colour blindness), mutations (point, frameshift, chromosomal), and genetic disorders — Mendelian (sickle-cell, thalassemia, PKU) and chromosomal (Down, Turner, Klinefelter syndromes). High-yield chapter for both Board (~8 marks) and NEET (~3-5 questions). Total: 17 sections including review sets.