- The Washington Times - Wednesday, March 16, 2005

The decoding of the human genome is giving rise to companies, often online, that do genetic home testing for the general public. It is causing a fair amount of howling in medical circles, yet shows every sign of continuing.

The prime example, which has been around for a while, is paternity testing. It is getting more sophisticated, though. A good example is GeneTree.com. If you are a man and worried that your child might not really be your child, you can go to the GeneTree site — or that of other companies that do the same thing — with your credit card.

Shortly a DNA collection kit arrives in the mail. It’s low tech: For example, it contains a cotton swab that you wipe across the inside of your cheek. You mail this, plus a sample from the child — blood, hair, saliva, what have you — to GeneTree. A week later, you get your answer online, if you choose. This currently costs $199.

The results of this peace-of-mind testing are unlikely to stand up in court, if it comes to that (says GeneTree itself). The reason is not the inaccuracy of the tests, but that courts want proof that the samples came from the persons they are said to have come from, that contamination didn’t occur, and so on. This is just normal evidentiary procedure. For a higher price, labs will usually do formal, legally acceptable tests.

A new wrinkle is genetic verification of percentage membership in racial groups. There are clubs, for example, for people who are of Native American descent, but how do you tell? With a genetic test. “AncestryByDNA 2.5: Determines what genetic percentage of Native American, European, East Asian, and African a person has, based on their autosomal DNA profile,” offers the GeneTree site.

Laboratories today can sometimes trace ancestry by sex. The reason is that certain DNA comes from only the mother, other DNA only from the father. Everyone has two sex chromosomes, X and Y, that determine the sex of the persons. A woman has two X chromosomes, and a man has one X and one Y chromosome. Thus, the DNA on the Y chromosome can only have come from the father.

Similarly, at conception, the father does not contribute mitochondria, which are energy-producing organelles in cells, to the fertilized egg. The mother does. Thus, mitochondrial DNA can only come from the mother.

Do-it-yourself genetics now goes well beyond paternity and ancestry. Companies such as www.dnadirect.com offer tests for risk of diseases such as cystic fibrosis and breast cancer. The prices vary, but tend to be in the hundreds.

The sales approach is, well, direct: “The Women’s Health Initiative found that women on hormone replacement therapy have double the risk of dangerous venous blood clots. If you have the factor V Leiden gene, this risk is even higher.”

Some doctors say — loudly — that these tests should not be allowed without the supervision of (surprise) a doctor. The argument is that ordinary people can’t interpret the results, might do the wrong thing, and so on. Although this argument isn’t wildly unreasonable, a cynic might suspect that the medical profession doesn’t want its revenue stream diverted.

The counterargument is that doctors aren’t geneticists. A specialist in reading DNA analyses will be better at it than a general practitioner who last studied genetics 20 years ago. Take your pick.

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