Question

Histones are a kind of protein that is known to play a very important role in packaging DNA into chromatin. What of the following characteristics about histones is true?

A. They are responsible for the methylation of DNA and switching on and off of genes
B. They are responsible for the supercoiling of DNA
C. They interact with DNA through covalent interactions
D. An octet of histones and a length of DNA forms a helix
E. They are responsible for helping topoisomerases bind to the DNA

Answer 1

Histones are basic proteins that bind to DNA and are responsible for the packaging of DNA into chromatin. They help regulate gene expression through their interactions with DNA and chemical modifications.

Step-by-step explanation:

Histones are basic proteins that bind to the acidic DNA backbone through their positively charged side chains, specifically lysine and arginine amino acids. The DNA wraps around an octamer of histones to form a structure called a nucleosome. Histones are responsible for the packaging of DNA into chromatin, which helps regulate gene expression and control the accessibility of DNA for transcription. This packaging is modulated by chemical modifications of histones, such as acetylation or methylation, which can alter the tightness of DNA wrapping and affect gene expression.

These nucleosomes further fold to create a higher order structure known as chromatin. Epigenetic modifications such as acetylation and methylation can alter the tightness of DNA wrapped around histones, thus regulating gene expression without altering the DNA sequence.