Question

Histones are rich in
(a) Alanine and glycine
(b) Cysteine and tyrosine
(c) Lysine and arginine
(d) Histidine

Answer 1

 Hint: Histones are proteins that help in the supercoiling of DNA to form nucleosomes. Since DNA is a negatively charged molecule, the histones are positively charged. They are rich in two essential amino acids that are basic in nature and hence provide positive charge to the histones.
Complete Step by Step Answer:
In eukaryotic cells, the DNA is wound around an octamer of a histone protein core to form nucleosomes. These histone proteins are rich in basic amino acids lysine and arginine. These amino acids give a positive charge to them which helps in the winding of the negatively charged DNA around the histone core.
- Histones are the chief protein components of chromatin as they act as the spools around which the DNA condenses and winds. Without the histones, unwound DNA would be very long.
- The histones are of 5 major types as follows:
- Four of them present in the octamer core are the H2A, H2B, H3 and H4. The octamer has two units of each of these proteins.
- Another histone called H1 or H5 is present too.

So, the correct answer is, “Lysine and arginine.”

Note:
- Histones were discovered by Albrecht Kossel in 1884.
- Both Lysine and Arginine are essential amino acids in children, that is they are not generated by the body and are needed to be supplemented in the diet. In adults, arginine is semi- essential i.e. it is partly secreted by the body.
- Arginine is an amino acid that can be used to treat heart and blood vessel conditions, while lysine is important for normal growth and turnover of muscle cells.