Understanding the embryology bill

Any attempt to overhaul the laws relating to embryo research and in vitro fertilisation treatment will be controversial, but it would have been hard to foresee the threats of cabinet minister resignations and the war of words that has broken out between leading religious and scientific figures.

So far, the furore over the Human Fertilisation and Embryology Bill has centred on the issue of creating mixed human and animal embryos for research. The leader of the Catholic Church in Scotland has described this as "Frankenstein science", while scientists have countered that he does not understand the facts and is "scaremongering".

Shortage of human eggs

Let's be clear. Although the headlines describe "hybrids", the bill acutally refers to human admixed embryos, which will most commonly be cybrids, such as where the genetic material is removed from a cow's egg and replaced with human material. Medical research is being hindered by the shortage of human eggs (since they cannot be donated without some risk), and this cybrid technique produces material that is 99.9 per cent human.

A chimera (mixing human and animal cells) and a true hybrid (fertilising a human egg with animal sperm or vice versa) would be permitted, but all research must be licensed by the Human Fertilisation and Embryology Authority, and it will be illegal to implant any mixed embryo in a human or other animal. Although calling it an embryo when fertilised is technically correct, some scientists complain that this conjures an image of a baby, while the reality is that they work with a cluster of perhaps 32 cells, no larger than a pinhead, which must be destroyed within 14 days.

Scientists say this research holds the prospect of cures for motor neurone disease, Parkinson's, and an array of other conditions, but it would be naive to expect a coldly rational debate on such an emotive issue. The idea of mixing a human and another animal was always going to capture the imagination, as it has from the earliest mythology through to modern fiction and superheroes.

In fact, the technique is already permitted under the existing legislation. A team in Newcastle has created a cybrid embryo and a team in London has a licence from the Human Fertilisation and Embryology Authority to do so, although the decision is being challenged in the courts by some Christian groups.

Societal change

The Human Fertilisation and Embryology Act 1990, rooted firmly in Baroness Warnock's report of 1985, has lasted remarkably well in the face of enormous technical and social change, but is clearly in need of revision. IVF has become widely accepted in the time that the world's first "test tube baby", Louise Brown, has grown up and become a mother herself. Controversy is more likely to focus on issues of access, such as NHS funding or the provision of IVF to single people or non-heterosexual couples.

Even so, the "yuk factor" can kick in when we push at the boundaries, such as with mixed embryo research, perhaps in the same way that the idea of developing face transplants provokes a reaction that we no longer feel for heart or kidney transplants.

Other emotive issues in the bill will no doubt take their turn as the focus of attention, including:

• the creation of so-called "saviour siblings" (in fact, like admixed embryos, these are already permissible but more closely regulated by the bill);

• the substitution of the need for "supportive parenting" for the existing "need for a father" test as a limit on access to IVF (allowing single people and non-heterosexual couples greater access);

• restrictions on sex selection and pre-implantation genetic diagnosis (already prompting one deaf couple to demand their right to select a deaf embryo).

• The bill may yet also be used as an opportunity to reopen a debate on abortion.