Ever wondered why identical twins become less alike as they age, even developing different diseases? Why are the cells of your skin so different from the cells of your kidneys, even though they contain exactly the same DNA? The answer lies in epigenetics, an extra layer of information on top of genes, that controls how the genetic script gets used. It’s the link between nature and nurture and it’s important in a huge range of biological processes. It explains why tortoiseshell cats are almost always female, and why global warming is leading to catastrophic skewing of the sex ratios in turtle populations.
Drug companies are investing billions of dollars in creating new therapies for cancer, using their knowledge of how epigenetic problems can drive this disease. Most weirdly of all, the epigenetic system can be a means by which responses to the environment get passed down through generations, without any change in DNA. It’s a wonderful, strange, fascinating and sometimes controversial science, and it affects us all.