Although IVF clinics are beginning to screen embryos so that children will not carry genes for diseases which appear late in life, their clients could be buying a pig in a poke. An article in the New York Times by Gina Kolata points out the link between genes and life expectancy and many diseases is very small, so small that it is nearly impossible to predict. "Recent studies find that genes may not be so important in determining how long someone will live and whether a person will get some diseases — except, perhaps, in some exceptionally long-lived families. That means it is generally impossible to predict how long a person will live based on how long the person’s relatives lived."

This has been confirmed by research on fraternal and identical twins. A 2000 study of 44,788 pairs of Scandinavian twins in the New England Journal of Medicine found that only a few cancers had a genetic component — and that was very small. Dr Robert Hoover, of the National Cancer Institute, wrote in an accompanying editorial: There is a low absolute probability that a cancer will develop in a person whose identical twin — a person with an identical genome and many similar exposures — has the same type of cancer. This should also be instructive to some scientists and others interested in individual risk assessment who believe that with enough information, it will be possible to predict accurately who will contract a disease and who will not."

Despite this, many people are prepared to sift through embryos until they find one which will have a long life. Twenty-eight per cent of American IVF clinics which test embryos have done it to avoid an adult-onset condition such as Huntington disease, hereditary breast cancer, or Alzheimer’s.

NEJM & STEM CELLS: the New England Journal of Medicine has again expressed its strong support for therapeutic cloning. The deputy editor of the prestigious journal, Dr Robert S. Schwartz, wrote in an official commentary in the current issue that ” Research on stem cells will encounter many twists and turns, but it is an endeavour that is eminently worth pursuing. The delay of medical advances by theological disputes is not in the best interests of the sick and disabled.”

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Michael Cook

Michael Cook edits BioEdge, a bioethics newsletter, and MercatorNet, an on-line magazine whose focus is human dignity. He writes from Sydney, Australia.

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