Chromosome : Definition, Structure and function
Chromosomes are deeply stained thread like structures within the nucleus of each animal cell.
Chromosomes number: 46 or 23 pairs
a. Autosomes 22 pairs
b. Sexchromosomes I pair (XX or XY).
Structure of chromosome
Each chromosomes is composed of a double helix of DNA along with histone and non-histone proteins The DNA-protein complex exists as a highly coiled or folded structure.
a. The non-h proteins are DNA and RNA polymerases, gene regulatory proteins and HMG (high mobility group) proteins.
b. The histones are the most abundant group of basic proteins which help packaging of chromosomal DNA. There are five histone proteins according to the concentration of arginine and lysine residues: HI,H2A, H2B, H3, and H4.
Chromosomes act ax carries of units of inheritance in the form of genes of nuclear DNA. Genes are borne by the chromosomes in linear series as pasts of specific DNA molecules.