Nova: Ghost in Your Genes

The vertebrae in which hoxc-6 is active (marked purple) in both a chick embryo and garter snake embryo.
The vertebrae in which hoxc-6 is active (marked purple) in both a chick embryo and garter snake embryo.
Although the title of the special made me think of ‘Party in Your Pants’ (juvenile, I’m well aware), I thought I’d post a link to the website for the Nova special, ‘Ghost in Your Genes.’

The special explores epigenetics and the complex network of regulatory mechanisms that affect gene expression, including a nice little slideshow on Hox genes. We’ve explored the topic before here at Neuroanthropology (see Pharyngula on epigenetics) in part because a better understanding of the molecular mechanisms of organic development tends to undermine the overly simplistic notion that there are two forces shaping any organism — genes and environment or ‘nature’ and ‘nurture.’ With the epigenetic material, it’s painfully obvious that genes are not some kind of organic destiny writ in DNA, as some popular understandings tend to have it (and that popular understanding is often mobilized in simplistic accounts of subjects like behavioural genetics, as we will know).

We’ve already discussed some of the quirks about twins’ genes here (at Identical twins not… err… identical?), and there’s a nice example of genetically identical twin mice looking anything but identical (and having significant differences in health). The story, ‘A Tale of Two Mice,’ has a sobering subtext about the effects on gene expression of BPA (Bisphenol A), an organic chemical known to leach out of plastics (see Wikipedia for a brief overview of the issues). However, I’m still not convinced that calling this complex interaction ‘the epigenome’ or ‘the second genome’ is moving in the right direction. Even with this reservation, the visual aids for thinking about epigenetic processes are excellent.

Thanks to Dr. Jovan Maud (from Macquarie University and Culture Matters) for pointing this piece out to me. Unfortunately, I just gave my lecture on this stuff a week and a half ago — I’m afraid that I confused my audience a lot more than the people at Nova. It’s a nice site though for getting a bit of a feel for the sorts of factors that affect gene expression.

The brilliant graphic accompanied a reprint of Sean B. Carroll’s article, ‘The Origins of Form: Ancient genes, recycled and repurposed, control embryonic development in organisms of striking diversity,’ originally published in Natural History, November 2005. Carroll’s article can be accessed here, and it’s a great entry-level piece on hox genes and basic ‘evo-devo’ thought, but the author of Endless Forms Most Beautiful.