Write a short note on Nucleosome

Nucleosome is the basic structural unit of the chromosome. It is bread- like structure of 55 A° height and 110 A° diameter. Its core is a octamer of histone proteins H2A, H2B, H3 and H4 and is wrapped by 13/4 turns of DNA (146 base pair long). It is also associated with a H1 protein molecule, which undergoes phosphorylation during packaging (chromosomal condensation).