Question

Nucleosome contains
A. H2A, H2B, H3, H4
B. H3, H4
C. H2 A, H2B, H3
D. HI, H2A, H2B, H3

Answer 1

Hint: Chromosome consists of DNA and protein. Major proteins in chromatin are histone proteins. These are meant for the packaging of DNA into the compact small nucleus. A nucleosome is considered as the repeating unit of eukaryotic chromatin.

Step by step answer:
Long DNA must fit into a small cell and a small nucleus of the cell. Hence, the packaging of DNA occurs.
In eukaryotes, histone provides structural support to chromosome long DNA wraps around the histone protein and forms the compact structure. Histones are positively charged proteins due to the presence of basic amino acids such as lysine and arginine, that strongly bind to the negatively charged DNA molecule. Nucleosomes are the smallest structural unit of chromatin. A single nucleosome consists of a 150 base pair of DNA sequences. Nucleosomes and linked DNA together are called chromatosomes. Nucleosomes are arranged like beads on a string, they fold themselves again and again and form dense chromosomes. Two turns of DNA wrap around 8 histone proteins from the nucleosome, this octamer of histone includes H2A, H2B, H3, and variants of histone. H1 histone protein acts as a linker protein between two nucleosomes binds to linker DNA.
Hence, the correct option is option A, H2A, H2B, H3, H4.

Additional information:
There is a solenoid model of folding in which a solenoid has 6 nucleosomes per turn. The solenoid has a size of 30nm in diameter. At places, where chromatin is loosely packed represents euchromatin while the places where chromatin is densely packed represent heterochromatin.

Note: H2A, H2B, H3, and H4 variants of histone are the core histone. A human cell has six feet long DNA packed into the nucleus with a diameter less than a human hair. By reducing position charge on histone protein binding with DNA reduced and this useful in the process of transcription. During the process of replication, histone dissociates and along with DNA these proteins also get replicated.