Epigenetics / saliva.

The first item on the programme is about the US Deep Impact spacecraft. The second is about epigenetics, in particular new work by Tim Spector, director of the Twin Studies Unit at St Thomas Hospital, which suggests that identical twins have more in common than just the same genes. The third item is about a new way of screening for disease based at the University of California, using saliva. The final item is about how the human vocal tract adapts to playing the digeridoo.