What makes two individuals different.? Less the genome sequence , which has a minor place but the epigenome , a set of chemical modifications, not encoded in DNA , which dictate how and when genes are expressed. There are many ways of epigenetic modification, which includes methylation of the DNA , histones that wind around DNA to create a packed cluster of chromosomes and the activation of small non coding RNA. DNA methylation reduces gene expression.
Katsnelson 2010 Genomics goes beyond DNA sequence Nature vol 465 p 145
- Martin Eastwood