How can dna methylation silence transcription? a-methyl-cpg-binding domain proteins bind methyl groups and promote heterochromatin. b-methyl-cpg binding domain proteins irreversibly bind methyl groups, blocking transcription. c-methyl-cpg-binding domain proteins methylate the promoter regions, blocking transcription. d-methyl-cpg-binding domain proteins bind methyl groups and promote euchromatin.

The correct answer is option A.

Explanation:

A procedure by which the methyl groups are added to the molecule of DNA is known as DNA methylation. DNA methylation generally functions to repress the transcription of the gene. The DNA methylation may influence the transcription of genes in two prime manners, of which one is the binding of the methylated DNA with the MBDs or methyl-CpG-binding domain proteins.  

In the process, the MBD proteins supplements additional proteins to the locus like histone deacetylases and the chromatin remodeling proteins, which can change histones, thus, producing inactive and compact chromatin known as heterochromatin.