Turned up to eleven: Fair and Balanced

Tuesday, July 09, 2002

On to more scientific matters. Gene Expression is the blog written by a consortium of science bloggers including my (and Charles Murtaugh's nemesis, "Godless Capitalist". In a recent post, GC cast aspersions on our arguments about racial differences, genetics, etc (this is old hat to the readers of this site, I expect). Nevertheless, I think that he mischaracterized both our arguments, and the issue in question. I responded in the comments on this post, but I want to go into more detail here.
Fundamentally, the argument is over the nature of complex traits (i.e., involving many interacting genes and environmental conditions), and how to describe them, understand them, and potentially alter them. GC would like to cast the argument in terms of "race rationalism" (his terminology), but the issue is far more fundamental than race (which is really just a special case). GC cites a study in recently published in brief in Nature about a long term selection experiment in fruit flies (Drosophila). The experiment is as follows. Set up a maze in which the entering fruit fly can get to the "prize" (food or whatever) based on a preference for going either up or down at a branch point. Setting up collection stations at the top and bottom of the maze, you can select for flies that prefer one or the other. Repeated inbreeding of those flies (i.e. "up" with "up", "down" with "down") results in strains with hereditary tendencies toward a behavior. This experiment is not different from breeding domesticated plants or animals, mechanically. Now, here comes the new stuff!

The authors, presented with the revolutionary genomic analysis tools of the DNA Microarray (which I have written about here) were able to identify a large cohort of genes that are involved in this behavior, by virtue of the fact that their expression level is different in the two strains. Now, GC, looking at this, decides that this is evidence that genetic understanding of complex traits is an inevitable consequence, and "gene tailoring" is part of our future. Murtaugh, on the other hand, sees something quite different. To summarize, Charles thinks that the investigators are admitting that the individual contributions are small, and that the only single factor of great relevance is environment (if I have his point wrong, he can correct me). The implication is that large groups of genes are involved, each contributing slightly to the overall phenotype.

A new blog thread evolves

An important point is the question of robustness. In other words, how stable is this phenotype to perturbations in the genetic makeup? If you knock out one of the genes, does it disappear? How many of the genes in the relevant group are like this, and how many are differentially relevant? How does a biologist start modelling a system with 250 constituents, interacting in unspecified ways with one another? How does a person (or, more likely, a large lab group) start dissecting and understanding such a system? I will try, in the next few days (weeks) to give some answers to these questions, and the implications for those answers on various "Brave New World" scenarios ala "Godless Capitalist".