Genes in CpP island is inactivated by:

Ans: a. Methylation[Ref Lippincott 6th/709; Harrison 19th/101e-4, 18th/668, 679; Robbins 9th/893; Satyanarayan 3rd/359, 572; Lippincott 4th/460-62; Chatterjea Shinde 7th/346, 426; en. wikipedia. org/wiki/DNA_methylationjCpG islands: Methylation of cytosine by a methyltransferase is associated with silencing of the activities of ceain gene"-Lippincott 6th/709Cytosine 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 general, methylation leads to loss of transcriptional activity & thus inactivation of genes.The role of epigenetic control mechanisms in the development of human cancer is unclear. However, a general decrease in the level of DNA methylation has been noted as a common change in cancer. In addition, numerous genes, including some tumor-suppressor genes, appear to become hypermethylated and silenced during tumorigenesis.