<unk>  is the study of<unk> modifications to the DNA of<unk>  cells that do not involve a change in the nucleotide sequence, but instead involve a change in the way the genetic code is expressed.<unk> mechanisms are necessary to maintain normal sequences of tissue specific gene expression and are crucial for normal development. They may be just as important, or even more important, than genetic mutations in a cell's transformation to<unk> . The disturbance of<unk> processes in<unk> s, can lead to a loss of expression of genes that occurs about 10 times more frequently by transcription silencing (caused by<unk> promoter hypermethylation of CpG islands) than by mutations. As Vogelstein et al. point out, in a colorectal<unk>  there are usually about 3 to 6 driver mutations and 33 to 66 hitchhiker or passenger mutations. However, in colon tumors compared to adjacent normal-appearing colonic mucosa, there are about 600 to 800 heavily methylated CpG islands in promoters of genes in the tumors while these CpG islands are not methylated in the adjacent mucosa. Manipulation of<unk> alterations holds great promise for<unk>  prevention, detection, and therapy. In different types of<unk> , a variety of<unk> mechanisms can be perturbed, such as silencing of tumor suppressor genes and activation of oncogenes by altered CpG island methylation patterns, histone modifications, and dysregulation of DNA binding proteins. Several medications which have<unk> impact are now used in several of these diseases.<unk>  patterns in a normal and<unk>  cells<unk> alterations in tumour progression
Cancer epigenetics
Cancer immunology
Cancer research
Human genetics
Human reproduction
Cancer systems biology
causes of Neoplasm
Human behaviour genetics