Question

Nu body of nucleosome consists of _________.
A.

and

B.

and

C.

and

D. Both [b] and [c]

Answer 1

Hint: A nucleosome is a segment of DNA that is encircled by a protein core. DNA may be compressed into a smaller volume within the nucleus by forming a combination with proteins known as chromatin. The structure of the expanded chromatin resembles beads on a thread when examined under a microscope.
Complete step-by-step solution:
A histone octamer, which is an eight-protein group called histones, surrounds a little less than two twists of DNA in each nucleosome. The histone proteins \[{H_2}A\], \[{H_2}B\], \[{H_3}\], and \[{H_4}\] each make up two copies of the histone octamer.

The eight-protein complex known as a histone octamer is what makes up the nucleosome core particle. When a tetramer, which has two copies of both \[{H_3}\] and \[{H_4}\], interacts with two \[{H_2}A/{H_2}B\] dimers, the octamer forms. Along with the linker DNA, the \[{H_1}\] histone protein, which is not a component of the nucleosome, joins the two nucleosomes.
Arginine and lysine are two of the positively charged amino acid residues that make up the majority of histones. Through electrostatic interactions, the positive charges enable them to form intimate associations with the negatively charged DNA. Histones are proteins that attach to DNA, form chromosomes and regulate gene activity.
Hence, option D is correct, i.e., Both [b] and [c] (\[{H_2}A\] and \[{H_2}B\],\[{H_3}\] and \[{H_4}\]).
Note: A nucleosome on a promoter stops transcription from starting. The majority of genomic DNA is associated with nucleosomes, which inhibits initiation from cryptic promoters. Thus, the nucleosome functions as a repressor of all transcription in addition to being a universal gene repressor (genic, intragenic, and intergenic).