Correct option is A
Explanation:
(1): Correct. The majority of histone modifications, such as acetylation, methylation, phosphorylation, and ubiquitination, predominantly occur at the N-terminal tail of histones. These modifications play a crucial role in the regulation of gene expression and chromatin structure.
(2): Incorrect. While modifications can occur at the C-terminal tail of histones, they are not as common or significant as those that occur at the N-terminal tail. The C-terminal tail is less involved in the regulation of chromatin structure and gene expression.
(3): Incorrect. The globular core of histones, which is the part that binds the DNA, is not primarily involved in histone modifications. Modifications are generally focused on the tails that extend from the core.
(4): Incorrect. Histone modifications do not occur equally throughout the polypeptide. They are concentrated on the N-terminal tails, where they serve as binding sites for various regulatory proteins involved in chromatin dynamics.
Information Booster:
The N-terminal tails of histones protrude from the core histone structure and are easily accessible for various modifications.
Histone modifications at the N-terminal tail play a key role in epigenetic regulation, affecting the compaction of chromatin and thus gene expression.
Common modifications like acetylation (which activates gene expression) and methylation (which can repress gene expression) mainly occur on the lysine residues of the N-terminal tails.
These modifications are often dynamic, responding to cellular signals and environmental cues, and contribute to chromatin remodeling.
