All are true about DNA methylation except:
Ans: (D) No role in carcinogenesisCytosine in the sequence CG of DNA gets methylated to form 5'-methylcytosine. A major poion of CG (about 20%) in human DNA exists in methylated form.In DNA, methylation usually occurs in the CpG islands, a CG rich region, upstream of the promoter region. In humans, DNA methylation is carried out by a group of enzymes called DNA methyltransferases.DNA methylation stably alters the gene expression pattern in cells such that cells can "remember where they have been" or decrease gene expressionDNA methylation is essential for normal development and is associated with a number of key processes including genomic imprinting, X-chromosome inactivation, suppression of repetitive elements, and carcinogenesis.Adenine or cytosine methylation is pa of the restriction modification system of many bacteria, in which specific DNA sequences are methylated periodically throughout the genome.Within the bacterium, methylation protects the host DNA from cleavage by its own restriction enzyme. Unmethylated foreign DNA is not protected from cleavage.
It usually occurs in the cytosine
Can alters the gene expression pattern in cells
Role in genomic imprinting
No role in carcinogenesis