Jenny Graves

We really think they're going to be humans around in 8 million years?

We've only been human for 200,000 years.

We've got a long ways to go.

Can you just tell me what that SRY gene is first?

Well, the SRY gene we know is the male determining gene and what it does is

is activates other genes that eventually produce a testis in the embryo at about 12 weeks after conception.

And the testis produces male hormones and it's the male hormones that make the baby a boy.

It's actually a very complicated pathway and it's full of checks and balances.

It turns on a gene called SOX9, but that gene doesn't do anything directly.

What it does is it suppresses genes that make an ovary.

So you think, why is it so complicated?

There's 68 genes that you need to be working, either pushing or pulling or towards a testis to be male.

And what that means is that there are people who have variations of some of these genes who may have SRY but are not male because another gene is either more active or less active or pushes too much or pushes too little.

And so we know of several variations of sex determination where you get XY genes.

females or XX males.

Now, these are generally fairly rare, but they do exist.

And there's one particularly that seems to be quite common in athletes, and that is babies that are born with a testis that makes androgens hormones, but the body can't use the androgens because the protein that receives it and activates it in the nucleus is

something different about it so it doesn't bind.

So they are girls, they're born girls, they're recognised as girls, but then it turns out that they actually have a Y chromosome and an SRY gene, but they're definitely not male.

So the IOC will have to know what the exceptional people are and make allowances for them.