Question

How are the following formed and involved in DNA packaging in a nucleus of a cell?

(i) Histone octomer
(ii) Nucleosome
(iii) Chromatin

Answer 1

(i) Histone octamer: It is a unit consisting of eight molecules of histone proteins (two molecules each of H2A, H2B, H3 and H4 histones). It interacts with the DNA to keep it associated with itself. 
(ii) Nucleosome: DNA (negatively charged) winds around the histone octamer (positively charged) to form a nucleosome, which acts as a building block for packaging the DNA into chromatin.
(iii) Chromatin: It is a complex of DNA and proteins. Its main function is to efficiently package the DNA into the nucleus.