Question

What chemical changes in histone proteins are responsible for changes in gene expression?

1) addition or removal of methyl and acetyl groups within the tail domains of histones
2) addition or removal of methyl and acetyl groups within the globular domains of histones
3) proteolytic cleavage of the globular and tail domains of histone proteins into oligopeptides
4) removal of electrically-charged functional groups from the tail domains of histones
5) addition of acidic groups and removal of alkaline groups within the tail domains of histones

Answer 1

Chemical changes in histones, like the addition or removal of methyl and acetyl groups within the tail domains, regulate gene expression by altering the tightness of DNA-histone binding.

Step-by-step explanation:

The chemical changes in histone proteins that are responsible for changes in gene expression include the addition or removal of methyl and acetyl groups within the tail domains of histones. These modifications influence how tightly DNA is wound around the histone proteins, thus affecting gene expression.

When chemical modifications such as the addition of acetyl groups occur, they neutralize some of the positive charge on the histones, making the DNA less tightly bound and more accessible for transcription. Conversely, the removal of acetyl groups or the addition of methyl groups can increase the positive charge and tighten the association with DNA, leading to decreased gene expression.