Which statement about DNA methylation and histone acetylation is accurate?

Which statement about DNA methylation and histone acetylation is accurate?

• A. DNA methylation generally activates transcription; histone acetylation tightens chromatin.
• B. DNA methylation generally represses transcription; histone acetylation loosens chromatin and increases transcription.
• C. DNA methylation has no effect on transcription; histone acetylation decreases transcription.
• D. DNA methylation always removes histone acetylation; gene expression is unaffected.

Answer: (B)

DNA methylation, especially at promoter CpG sites, tends to repress transcription because methylated DNA recruits proteins that compact chromatin and block transcription factor binding. Histone acetylation adds acetyl groups to lysine residues on histone tails, which neutralizes positive charges, loosens DNA–histone interactions, and creates a more open chromatin structure that enables transcription machinery to access the DNA. So, methylation generally represses transcription while acetylation loosens chromatin and promotes transcription. While there are exceptions in specific contexts, this combination best reflects common regulatory patterns.

DNA methylation, especially at promoter CpG sites, tends to repress transcription because methylated DNA recruits proteins that compact chromatin and block transcription factor binding. Histone acetylation adds acetyl groups to lysine residues on histone tails, which neutralizes positive charges, loosens DNA–histone interactions, and creates a more open chromatin structure that enables transcription machinery to access the DNA. So, methylation generally represses transcription while acetylation loosens chromatin and promotes transcription. While there are exceptions in specific contexts, this combination best reflects common regulatory patterns.