[Campbell Biology P.420] Which of the following statements correctly distinguishes between h... | Practice Question

Which of the following statements correctly distinguishes between histone methylation and DNA methylation in the context of gene expression regulation?

  • A: Both histone methylation and DNA methylation generally lead to increased gene transcription.
  • B: Histone methylation modifies the DNA sequence, while DNA methylation modifies histone proteins.
  • C: Histone methylation affects the accessibility of DNA by condensing chromatin, whereas DNA methylation directly silences genes by adding methyl groups to DNA bases.
  • D: DNA methylation is specific to mammalian X chromosomes, while histone methylation occurs in all eukaryotes.

Explanation

Histone methylation, the addition of methyl groups to histones, can lead to chromatin condensation and reduced transcription. DNA methylation involves the methylation of DNA itself, usually cytosine, and is associated with inactive DNA regions. While an example given is mammalian X chromosomes, it occurs broadly in plants, animals, and fungi.