Professor Sykes discusses embryonigical development

Professor Sykes:
There is no doubt that amongst mammals, anyway, the natural cause of embryonigical development goes into the female. And what happens, what stops an embryo from becoming female is this thing called the "y chromosome". And it has on it (actually we now know exactly) 27 genes on it.

One of these genes is like a little genetic switch that switches on around about six or seven weeks of embryonic life after fertilisation and brings about a whole cascade of changes. It's like a relay really - which switches on, and that switches on to something else, and that switches on to a couple of things, and so on. There's a whole cascade of changes that begin to produce, for example, male hormones and then they change the anatomy of the embryos so that eventually it comes out as a boy.

And the other 26 genes that are on the "y chromosome" are concerned with (we don't quite know what they do), but they're concerned with, for example, the production of sperm. Now the "y chromosome" when you look at it under the microscope is very short and it used to be as ancestor - we can now tell again by comparing dna certainties. It used to be a much bigger chromosome called the "x chromosome". Actually, men and women have "x chromosomes" but men have one, women have two. And actually in women, only one of those is working. So it's got thousands of genes on it.

The "y chromosome", on the other hand, has lost most of it's genes, it's just got these few stragglers left. And I'm not along amongst geneticists to be absolute convinced that the "y chromosome" is going to become extinct soon and the reason for this is if you look, again, at the sequences of the "y chromosome" you can see that it's riddled with mutations, absolutely riddled with mutations.