Question

Histone occupies the major grooves of DNA at an angle of
A. \[{15^ \circ }\]
B. \[{90^ \circ }\]
C. \[{45^ \circ }\] to the helix axis
D. \[{30^ \circ }\] to the helix axis

Answer 1

Hint: Histones are positively charged proteins of chromosomes. Histones in the nucleus serve a purpose to support the chromosome and bind with the large elongated DNA as the DNA are negatively-charged molecules they combine to form nucleosomes by providing the space for DNA to arrange in a compact form.

Complete answer: The structure of DNA is a double helix and the DNA wraps around Histone molecules for packaging.
We can observe two types of grooves in the double helix structure of DNA.
One is a minor groove and the other one is a major groove.
Minor groove is the small groove as the distance difference between each helix is small.
So option A is not correct as the angle is minor.
The major groove is the distance difference between each helix is large.
Option B is not correct as the angle is too large.
Option C \[{45^ \circ }\] is not correct, as the helix axis is large distance as the DNA to be closely packed at such a large angle is not preferred. Till 30° is moderately considered to form a compact structure of DNA around Histone protein.
The angel in the major groove of DNA along with Histones is nearly \[{30^ \circ }\]
So, the correct answer is “Option D”.

Note:
Histone proteins are also responsible for gene expression. The gene information is passed within the cells due to the compact arrangement of the DNA. Hence without the Histone, there is no proper arrangement of the DNA within the cell and no passage of genetic information which could cause a complete imbalance in the nucleus.