DIFFERENCES between individuals are usually put down to variations in their genes. But altering the activity of a gene can make just as much difference as changing its sequence. The task of regulating gene activity falls to molecules that lock onto DNA, such as methyl groups.
This “epigenetic” control is now implicated in several disorders. With a few genes, for example, the version inherited from the father must be switched on, and the maternal copy turned off. Called imprinting, this phenomenon is mediated by methylation, and if it goes awry it can cause disease. Imprinting errors are thought to cause abnormalities in cloned animals, and there are hints that IVF babies may…
