Why sex is a better way than cloning for human reproduction
Mon, Jan 19, 1998, 00:00
DR WILLIAM REVILLE
Well, it didn't take long, did it? The ink is scarcely dry on the report of the cloning of Dolly the sheep and now we have the American Dr Richard Seed, who wants to clone human beings within two years. He believes this will be the first serious step in becoming "`one with God". Dr Seed's proposal is outrageous. The debate on the ethics of human cloning has scarcely begun.
Even if human cloning was ethically acceptable, it is wildly premature from a technical point of view. In any event, human cloning would offend against the sound biological sense of sexual reproduction.
Two organisms are defined as clones of each other if they are genetically identical. Cloning occurs commonly in nature by an asexual process. When an amoeba wishes to reproduce, it simply duplicates its genetic material and divides into two daughter cells, each of whom receives an identical copy of the parent's genes. The daughters are clones of the parent.
Mammals produce offspring by sexual means. Mammals contain body (somatic) cells - liver, muscle, etc. - and sex cells - sperm in men, eggs in women. Every somatic cell contains a double set of genes, one from the father, and one from the mother. The sex cell contains only a single set of genes, some from the father, some from the mother. When a sperm fertilises an egg, the somatic cells of the offspring again contain full sets of genes from both parents.
Sex fulfils several important biological functions. It generates variety by combining characteristics of different people, vital raw material for natural selection, which is the engine of evolution. Because genes are so important, they must be repaired when they become damaged. If the damage is not repaired it must be hidden.
Sexual reproduction plays a vital role in this genetic hygiene. During the sexual process, repairs are made to damaged genetic material. Also, existing damage (mutations) that has evaded the repair machinery can usually be masked. The offspring contains a full set of genes from both parents for all characteristics.
Let us say the mother has a damaged gene for characteristic X. The likelihood is that the father's gene for X is good. The child will therefore have one good gene for X, which is usually sufficient to produce a normal X characteristic.
None of the genetic advantages of sex applies to reproduction by cloning. Sex between brother and sister is taboo because of the greatly increased likelihood that both will have damaged genes for the same characteristics, masked in each, but coming together in the offspring to produce a sick child. Cloning would be the ultimate incestuous relationship, whereby, in effect, you would marry yourself. It should never be introduced, therefore, as a widespread option for human reproduction.
Dr Seed proposes to use the Dolly technique to clone human beings. Briefly, Dolly was cloned as follows: a cell was taken from the adult Dolly's udder and its nucleus (containing the hereditary material) was removed. An egg cell was taken from a second sheep, and its nucleus was replaced by Dolly's nucleus. This egg cell, bearing Dolly's genes, was implanted in the womb of a third sheep, who duly produced the famous lamb in due course.
But the above story is incomplete. It describes the case that worked, not the many that failed. Many nuclei were inserted into many egg cells to produce embryos that were implanted into ewes. There was a high rate of miscarriage; 227 transferred adult nuclei were tried to produce one healthy lamb.
It is, therefore, from a technical point of view alone, far too early to carry out human cloning. The high failure rate would be unacceptable in a human context. Also, before cloning could be seriously contemplated for humans, extensive work would need to be done on a species that is much closer to humans than sheep, e.g., the chimpanzee.
But the whole idea of cloning human beings now is outrageous anyway because ethical norms have not been established in this area. It is not at all clear whether cloning of human beings will ever be ethically permissible, under any circumstances.
Public opinion is completely opposed to the idea of human cloning. If a maverick scientist produced a human clone there would be a massive public outcry. Science as a whole would be blamed for "sinning against nature" and politicians would be forced to introduce draconian controls on all sorts of scientific research.
Dr Seed wants to clone human beings in order to help infertile people. Of course infertile people should be helped, and a variety of widely acceptable means is already available, ranging from adoption to in-vitro fertilisation techniques. To suggest the problem of infertility is so desperately urgent that we must rush headlong at human cloning before we are ethically and technically ready, or rationally convinced, is monstrously ludicrous.
In the USA, President Clinton has instituted a five-year moratorium on research into human cloning in federal-funded programmes and has asked for a similar moratorium on a voluntary basis in non-federal agencies. Dr Seed is prepared to move to another state in order to carry out his plan. It is to be hoped that Dr Seed's scientific colleagues will be able to persuade him to desist. If not, more effective methods will have to be employed.
William Reville is a senior lecturer in biochemistry at UCC.
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