In General, When Cytosine Bases in CpG Islands are Methylated

Question

In general, when cytosine bases in CpG islands are methylated:
A)transcription is active and rapid.
B)transcription is active, but slow.
C)transcription is repressed.
D)translation is active and rapid.
E)translation is repressed.

Accepted Answer

Methylation of cytosine bases in CpG islands is a mechanism for gene silencing or transcriptional repression. When this occurs, the enzyme methyltransferase adds a methyl group to the cytosine, and transcription factors are unable to bind to the DNA, resulting in less gene expression or transcription. Therefore, the correct answer is C) transcription is repressed.