1. Eukaryotic cell DNA (2.2 meters) undergoes condensation, coiling, and supercoiling for efficient packaging in the nucleus (10-16 meters).
2. DNA associates with both histone and non-histone proteins.
3. Histones, positively charged basic proteins, are rich in lysine and arginine amino acid residues.
4. The nucleosome consists of a nucleosome core with two molecules each of histone proteins (H2A, H2B, H3, and H4) forming a histone octamer. The DNA (146 bps) wraps around the octamer by 1 3/4 turns.
5. H1 protein binds the DNA thread at the entry and exit points of the nucleosome.
6. Linker DNA (varying from 8 to 114 bp, averaging about 54 bp) connects adjacent nucleosomes.
7. Each nucleosome contains 200 bp of DNA.
8. Packaging involves the formation of structures like Beads on a string (10 nm diameter), Solenoid fiber (resembling coiled telephone wire, 30 nm diameter/300Å), Chromatin fiber, and Chromosome.
9. Non-Histone Chromosomal Proteins (NHC) play a role in packaging chromatin at a higher organizational level.