Review by Amy Evans
This episode of the Radio 4 series Inside Science, presented by Adam Rutherford, offers some useful insights into the Y chromosome, and might be helpful when revising. The 6 minute clip tells you all the basic facts that outline sex determination in humans in a short amount of time.
In the segment, Rutherford interviews Henrik Kaessmann from Heidelberg, lead author on two newly published Nature papers on the evolution of the Y chromosome (see Origins and functional evolution of Y chromosomes across mammals and Mammalian Y chromosomes retain widely expressed dosage-sensitive regulators.
The Y chromosome’s primary purpose is to override the default sex setting, which is female, since it carries the SRY gene. According to Kaessmann, the Y chromosome (and also the X chromosome) were originally autosomes (i.e. ordinary chromosome of which we have two copies) and evolved to become sex chromosomes. This limited role explains why the Y chromosome is ‘losing’ genes; because it only needs to retain the genes needed in sex determination and other male specific functions. Despite this, Kaessmann suggests that the Y chromosome has actually been stable for 25 million years and this ‘decaying’ of the Y chromosome is actually the Y chromosome evolving. As well as male-specific genes it has been shown that the Y chromosome also retains some regulatory genes. The exact function of these genes is presently unknown, but they seem to be essential in processes other than development.
After talking about the Y chromosome the rest of the programme (which can be found at this link) also covers information on avalanches, aphids, lichens and the longitude problems.