Question

A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture. In one set of experiments, she succeeded in increasing acetylation of histone tails in the chromatin of the cells. Which of the following results would she most likely see in these cells?
A) increased chromatin condensation
B) decreased chromatin condensation
C) decreased binding of transcription factors
D) inactivation of the selected genes

Answer 1

Answer:

B) decreased chromatin condensation

Explanation:

The addition of acetyl groups to the histone tails results in a less packed state of chromatin. The acetylation of multiple Lys residues in the amino-terminal domains of histones H3 and H4 reduces the affinity of the entire nucleosome for DNA. It occurs since acetylation reduces the total positive charge present on histone proteins. Histone proteins are positively charged and pack the negatively charged DNA around them. Therefore, increased acetylation results in decreased condensation of chromatin. The loosely packed DNA is accessible by RNA polymerase and transcription factors for gene expression.