Genetic code- inventory of linkages between nucleotide triplets and the amino acids they code for A gene is a segment of RNA that brings about transcription of a segment of RNA Transcription vs. Translation Review Transcription Process by which genetic information encoded in DNA is copied onto messenger RNA Occurs in the nucleus DNA mRNA ... DNA methylation is an epigenetic mechanism that occurs by the addition of a methyl (CH 3) group to DNA, thereby often modifying the function of the genes and affecting gene expression. The most widely characterized DNA methylation process is the covalent addition of the methyl group at the 5-carbon of the cytosine ring resulting in 5 ...