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What is CG islands in our DNA are impoant for: and explain in detail?
Ans: A. Methylation(Ref Harper 30/e p438, 439; Harrison 19/e p102e-7)CG islands:Also referred as "CpG islands".Plays vital role in gene expression regulation.Cytosine (C) residues in CG rich islands undergo methylation by DNA methyl transferase.The DNA methyltransferase can methylate only the CG sequence paired with methylated CG. The CG sequence not paired with methylated CG will not be methylated.Methylation of deoxycytidine residues (in sequence 5'-in CpG-3') in DNA may effect gross changes in chromatin so as to preclude its active transcription.