Which of the following does not or permissive euchromatin due to changes occurring at cytosine residues at CpG islands in DNA?
Methylation
Alkylation
Phosphorylation
Sumoylation
Ans: A. Methylationref: Harper's illustrated biochemistry, 30th editon., pg. 560.Methylation of cpG sites in the promoter of a gene may inhibit gene expression.There is also evidence that low folate status results in impaired methylation of cpG islands in DNA, which is a factor in the development of colorectal and other cancers.