What is epigenetics?

I think understanding the basics of inheritance is pretty easy for most people - the traits of parents are passed down from parents to offspring. Simple! Humans have known and exploited this fact for thousands of years. When Gregor Mendel came along, he meticulously worked out some mathematical rules for inheritance in peas, and we now know that these rules work (more or less) from plants, to ants to elephants, and we know the molecular basis lies in the replication and transmission of DNA. There's far more nuance than you learn in basic biology, of course. Most visible traits aren't governed by a single gene the way Mendel saw in his peas. Even human eye color - which is often touted as an easy one to understand - is polygenic. And of course there are characteristics that are heavily influenced by the environment. But still, heritable traits depend on genes, and genes are made of DNA, and the way DNA is divided up and passed on to offspring more or less follows the rules Mendel worked out over a hundred years ago.

That is, until we start talking about epigenetics, which is all kinds of confusing. So where to start?

You could try your hand at this recent nature article. It's behind a paywall, but that's probably a good thing. I can barely penetrate the jargon, and I'm a biologist:

The cells in a multicellular organism have nominally identical DNA sequences (and therefore the same genetic instruction sets), yet maintain different terminal phenotypes. This nongenetic cellular memory, which records developmental and environmental cues (and alternative cell states in unicellular organisms), is the basis of epi-(above)-genetics.


You could check out wikipedia, but I'm not sure they're much better:

In biology, and specifically genetics, epigenetics is the study of inherited changes in phenotype (appearance) or gene expression caused by mechanisms other than changes in the underlying DNA sequence, hence the name epi- (Greek: επί- over, above) -genetics. These changes may remain through cell divisions for the remainder of the cell's life and may also last for multiple generations. However, there is no change in the underlying DNA sequence of the organism;[1] instead, non-genetic factors cause the organism's genes to behave (or "express themselves") differently.

Get it? Me neither. To be fair the wikipedia entry has a lot of information, and it's about as well written as an encyclopedia article could be on a topic this complex, but if you don't have a background in biology, I don't know that it would get you very far.

If it's written information you're looking for, I think you're far better off reading ERV or PZ or Carl Zimmer. But, if you want a totally basic intro, that doesn't presume any prior knowledge, and you prefer curling up in front of a TV or computer to reading a multi-page article, then check out the recent lecture from Science in the News!

It's basic, but entertaining, and I learned some sweet stuff too. Enjoy!

2010 Fall Lecture 3.1: You Are What Your Mother Ate: The New Science of Epigenetics from Science in the News on Vimeo.

Part 2: Epigenetics and Us

Part 3: Epigenetics - Past, Present, and Future