Which statement best describes DNA methylation in gene regulation?

• A. It changes the DNA sequence.
• B. It can suppress transcription when present at promoter regions.
• C. It always enhances transcription.
• D. It only occurs in prokaryotes.

Answer: (B)

DNA methylation is an epigenetic modification where a methyl group is added to cytosine bases, usually at CpG sites. When promoter regions are methylated, transcription is typically suppressed because the added methyl groups can block transcription factor binding and recruit proteins that compact chromatin, making the DNA less accessible for transcription. This effect helps regulate gene activity without changing the DNA sequence, and methylation patterns can be inherited through cell divisions and change during development or in response to environmental cues. It’s not restricted to prokaryotes, and it doesn’t universally enhance transcription, so the statement that promoter-associated methylation can suppress transcription best describes its role in gene regulation.