Jones - DNA methylation

One epigenetic mark that we measure particularly commonly in human populations is DNA methylation. And DNA methylation is the addition of a small chemical group called a methyl group to DNA. It doesn’t change the DNA sequence, sequence stays the same but we get addition of this little methylation marks. In general, adding these methylation marks, especially the beginning of genes, so where the genes start is associated with turning that gene down.

So if we think about DNA methylation as a dimmer switch, the more methylation you add to the beginning of these genes, the lower the dimmer switch becomes until it can be turned completely off. And so DNA methylation changes that occur due to environments can alter these dimmer switches but they can also alter dimmer switches of genes that won’t necessarily affect how the gene is expressed right now. But might affect how it’s expressed given a different stimulus or a different exposure later on.

So it could be something – it could be called priming. It can prime a gene. You have a DNA methylation change due to exposure that actually doesn’t change what happens right now but it primes that gene so it sees a different exposure or something else or even the same exposure later on. The dimmer switch might influence the level of that gene expressed due to that second exposure.