Igor, throw that switch.

This week's New Scientist contains an article that makes me uneasy.

It's about turning male cells into eggs and female cells into sperm, in humans. You don't get to see the whole article unless you subscribe, but most libraries should have the magazine.

Why are they doing this? So that same-sex couples can have children that are genetically entirely theirs. No problem with that, you might think. Indeed, I have no moral objections at all.

My worries are scientific. Women have two X chromosomes. Men have one X and one Y. For lesbian couples there's no problem. Any child will be female because any combination gives two X chromosomes. Boys can't happen in that scenario. The lesbians also get a better deal since one of them can carry the child to term. Gay men would need a surrogate mother and that can lead to all kinds of other issues.

Consider what can happen if a male cell is used to produce an egg. It might have an X chromosome in it or it might have a Y. Likewise, male sperm might be X or Y. A natural female egg always has an X. It's the father's sperm that determines male or female.

If the egg is X, then the sex of the child is determined by whether the sperm that 'wins' is X or Y.

If the egg is Y, the child will definitely be male. He could be a mild oddity, a Y egg fertilised by an X sperm but that's not likely to cause him any serious problems.

If a Y sperm fertilises a Y egg, the ensuing problems are huge. The X chromosome does a lot of important things. The child will be a YY boy, he'll be a haemophiliac, he won't see red or green at all, and he's generally going to be very sick indeed. If he survives at all.

This should be avoidable. Agricultural scientists can separate bull semen for artificial insemination purposes, so that dairy herds get mostly cows and beef herds mostly bulls. It's possible to apply the same thing to humans. However, it's not infallible and it remains a risk that such a disastrously sickly child will be born.

Now, I'm not religious, nor do I care at all whether anyone around me is gay or straight. I have no moral standpoint to defend here. I just think this kind of meddling is going too far. It's the sort of thing that gives science the Frankenstein feel. It brings on the 'playing God' accusations and leads to censure of science. If one of those really sick YY kids ever emerges, how will science defend against accusations of 'Frankenstein' when the monster is there for all to see?

It seems unneccessary when orphanages are filled with children hoping to be adopted. I know some have objections to gay couples adopting, but I don't see why. Gayness isn't catching. The child isn't going to 'turn' just because his or her adopted parents happen to be the same sex. If I was an orphan I'm sure I'd rather be with a couple, same sex or otherwise, than stuck in some orphanage like a modern Oliver Twist. I'd still have plastered my room with Kate Bush posters, not George Michael. I'm confident it wouldn't have changed me.

Let the adoptee have a say. If the child has no objections, why should anyone else?

Why risk the potential birth-defects and possible terrible outcomes of this kind of dabbling with life, when it's really not needed? Aside from the X-Y issues, there are developmental aspects in embryo growth that egg cells can do, and which skin cells cannot. There is far too much potential for something to go horribly wrong. That's not fair to the child and it's not fair to the parents who have been given such high hopes.

Currently, homosexual couples can't have a child that's genetically theirs. Many heterosexual couples can't do that either. The current solution is adoption and that helps both the childless couple and the parentless child. Why meddle?

There's more to science than 'we can do this'. There's also 'should we be doing this?'

Frankenstein didn't ask that last question, and it didn't turn out too well for him.