Question

How does methylation of histone tails affect the accessibility of DNA? Choose one:

A. It relaxes the chromatin to make DNA more accessible.
B. It compacts the chromatin to make DNA less accessible
C. It can have different effects depending on the location.
D. Histone methylation has no effect on chromatin.

Answer 1

Histone methylation on specific residues can result in either the tightening or loosening of chromatin structure, thereby affecting DNA accessibility and gene expression.

Step-by-step explanation:

Methylation of histone tails can have different effects on the accessibility of DNA depending on where the methylation occurs. Generally, histone methylation can lead to both the compaction or relaxation of chromatin, affecting gene expression. For instance, methylation at certain lysine or arginine residues on histone H3 and H4 can either open DNA for transcription or, conversely, result in transcriptional suppression when other specific residues are methylated. These modifications are crucial for regulating gene activity, as they change the spacing of nucleosomes, which in turn impacts the accessibility of DNA for transcription.

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