When DNA is compacted by histones into 10-nm and 30-nm fibers, the DNA is unable to interact with proteins required for gene expression. Therefore, to allow for these proteins to act, the chromatin must constantly alter its structure. Which processes contribute to this dynamic activity?
A) DNA supercoiling at or around H1
B) methylation and phosphorylation of histone tails
C) hydrolysis of DNA molecules where they are wrapped around the nucleosome core
D) accessibility of heterochromatin to phosphorylating enzymes
E) nucleotide excision and reconstruction

Question

Quizplus · Accepted Answer

Methylation and phosphorylation of histone tails contribute to dynamic activity of chromatin by altering the charge and structure of the histone tail, which ultimately affects the overall structure of chromatin. This modification can either activate or repress gene expression by creating or blocking binding sites for transcription factors. The other options listed (A, C, D, and E) are not correct as DNA supercoiling, hydrolysis of DNA molecules, accessibility of heterochromatin, and nucleotide excision and reconstruction do not directly contribute to the dynamic activity of chromatin.

When DNA Is Compacted by Histones into 10-Nm and 30-Nm