Pharyngula on epigenetics
Posted by gregdowney on July 23, 2008
P. Z. Myers of Pharyngula, when he isn’t driving creationists into paroxysms, can write some great translations of biological concepts for the average reader. He does this in the post, Epigenetics, where he points out some of the problems with textbook definitions of the term. I really recommend checking this post out, but get a cup of coffee and a comfortable seat before you do — the post is not lite fare.
Epigenetics, although devilishly difficult, is absolutely essential for breaking with the common conception of DNA as ‘blueprint’ or marching orders for biological processes. In biological developmental processes, the expression of DNA is quite a bit more interesting than just ‘genes made it happen.’ Myers lays out a host of good examples, such as the variable degree to which histones permit or inhibit DNA transcription, the inactivation of parts of DNA when methylated, how chromosome geometric arrangement might affect gene expression, and other factors. He also discusses X chromosome inactivation in females (because they have two, one has to shut down), genomic imprinting on non-sex chromosomes (Myers discusses chromosome 15 and some of the disorders that can result), and disease changes in genetic expression (such as liver cirrhosis and retroviral insertions, which I touched on in an earlier posts on ‘identical’ twins).
Grunt Doc joked in the last Grand Rounds blog carnival that he hoped our post on psychiatric genetics ‘wouldn’t be on the test’; that goes double for the material Myers is covering. Fascinating, but, wow, tough to wrap the head around. But it’s already making me look at our calico cats in a new light…