CORE Genetic code, chromosomes and inheritance
Genetics begins with the movement of information from DNA to RNA to protein. DNA stores hereditary information in four bases, and a triplet codon links three bases with one amino acid or a stop signal during protein synthesis. Har Gobind Khorana — Genetic Code is the Indian-origin Nobel anchor: in 1968 he shared the Nobel Prize in Physiology or Medicine with Marshall Nirenberg and Robert Holley for interpreting the genetic code and its function in protein synthesis. Venkatraman Ramakrishnan — Ribosome structure is the second Nobel bridge: the 2009 Chemistry prize recognised studies of ribosome structure and function, which links codons with the ribosome that reads messenger RNA. Chromosomes package DNA; humans have 46 chromosomes in 23 pairs, and an extra copy of chromosome 21 produces trisomy 21, the chromosomal basis of Down syndrome. DNA fingerprinting rests on polymorphic DNA regions, especially short tandem repeats and variable number tandem repeats, not on blood group or fingerprint ridge patterns. Rajasthan enters this section through medical genetics: sickle-cell disease screening is relevant in tribal belts of Banswara, Dungarpur, Udaipur and Pratapgarh, where inherited haemoglobin variants matter in public health. At the conceptual level, mutation changes DNA sequence, allele names alternative gene forms, genotype names genetic constitution, and phenotype names visible expression shaped by genes and environment.