Sunday, September 02, 2007

Selection of performance-enhancing genes

In May, scientists at the NIH published an article about the genetics underlying extremely muscled "bully" whippets. They described a mutation in the myostatin gene that impairs myostatin's usual role of putting a brake on muscle development. Animals have two copies of most genes. Animals with this mutation in one of their myostatin genes (like the middle dog in the picture above) are heavily muscled and extremely fast. Animals with the mutation in both their myostatin genes , like the right dog in the picture, are barely recognizable as whippets. I think their extreme appearance contributes to the sense of alarm this discovery has occasioned.

There's a New York Times article on the subject that does a good job of describing the problems and benefits associated with identification of genes underlying given traits. I especially like this comment about the psychological effect:

Inborn abilities once attributed to something rather mystical seem to lose a certain standing when connected to specific genes.

There were several missteps in the article though. The author does not remark upon some fallacious breeder assertions. For example, she paraphrases breeders as saying "no genetic test can predict the intangible qualities that make a dog great." "Great" in this context seems to mean a racing champion. Why would we think the drive to win races not genetically based? In other kinds of animals, we've already identified genes that affect memory, sexual orientation, aggression and feeding.

A more elementary error in the article is the assertion that DNA testing will allow breeders to intentionally breed dogs with "a genetic advantage," as if breeders who have breed fast dogs together in the past have had conferred some other kind of advantage on the dogs. As long as people have selectively bred dogs, we have been manipulating the genetics of dogs, just without the level of knowledge we now have.

Still, I am pleased to see this kind of coverage in the popular media. And I too am somewhat sad about reducing canine and human qualities to genetics. However, both species have tens of thousands of genes, most traits are affected by multiple genes, and we cannot selectively breed canines or ourselves for many genes at a time at this point. We may prioritize some traits in either species, reducing our sense of mystery or the divine, but we will not eradicate quirkiness or the unexpected from either population any time soon.

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