DNA Methylation

Methylation of cytosine followed by a guanine
Methylation of cytosine followed by a guanine


cytosine O / O—P —O—CH2 guanine II o O I A In the DNA of differentiated cells, a methyl group (red) is most often attached to a cytosine that is fol— lowed by a guanine. H \ NH2 B A model of DNA shows methyl groups (red) attached to a cytosine—guanine pair on complementary DNA strands. When the cytosine on one strand is methylated, enzymes methylate the cytosine on the other strand. This is why a methylation tends to persist in a cell’s descendants.