single-locus vs multi-locus models?

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SelfishGene
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single-locus vs multi-locus models?

Post by SelfishGene » Fri Nov 19, 2010 5:51 am

I am having trouble understanding the following paragraph in The Extended Phenotype. Can someone Please explain what you think Dawkins means by "single-locus models" and "multi-locus models"?

My guess is that in the "single-locus model" the gene is defined as a single cistron, while in the "multi-locus model" a gene is considered as any stretch of DNA on the chromosome. But I could be completely mistaken. Thanks in advanced for the help.

"A related point is that the use of single-locus models is just a conceptual convenience, and this is true of adaptive hypotheses in exactly the same way as it is true of ordinary population genetic models. When we use single-gene language in our adaptive hypotheses, we do not intend to make a point about single-gene models as against multi-gene models. We are usually making a point about gene models as against non-gene models, for example as against “good of the species” models. Since it is difficult enough convincing people that they ought to think in genetic terms at all rather than in terms of, say, the good of the species, there is no sense in making things even more difficult by trying to handle the complexities of many loci at the outset. What Lloyd (1979) calls the OGAM (one gene analysis model) is, of course, not the last word in genetic accuracy. Of course we shall eventually have to face up to multi-locus complexity. But the OGAM is vastly preferable to modes of adaptive reasoning that forget about genes altogether, and this is the only point I am trying to make at present."

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JackBean
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Post by JackBean » Fri Nov 19, 2010 6:33 am

I think he doesn't mean any stretch of DNA, but rather these specific ones, which code for orthologs in one species. I.e. you are looking for genes with the same function. There is a nice graph, I think in Albert's The Cell, where he shows, that most of the genes belong to some multiple-gene family, that is you have several genes with "the same" function. In quotes, because they are usually expressed in other organs or enviroment (like stress; nutrition etc.), so their function is not truly redundant, but could be substituted with other members of that family.
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.

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