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Published online 20 February 2008 | Nature 451, 876 (2008) | doi:10.1038/451876a
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On the origin of deleterious mutations
Interpretation is key when it comes to population-genetics studies.
A genetic study into Americans of European or African descent finds that the Europeans have a bigger proportion of 'harmful' genes than the Africans. But the conclusion has already been questioned in one of what many expect to be a fresh wave of conflicts over data interpretation as new technologies enable a glut of population-genetics studies.
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I wonder about the assumption that the non-synonymous changes are deleterious. Maybe reducing the activity of protein is selectively advantageous. Or, perhaps the alteration changes the substrate specificity of the protein in a way that is also selectively positive. Think about the HbS mutations.
Iwonder at the sample size. This is a start and any conclusions based on such a small sample are premature at best.
In addition to the question of sample size and admixture in African Americans, it is important to reinforce what Gary has said. Mutations are only helpful or harmful within an environmental context and other polymorphisms in the genome. Even with a large sample size a conclusion would be difficult to draw.
I find it worrying that Geneticists have to be so careful about highlighting differences between populations/race groups. It's a fascinating subject. Discrimination does not necessarily mean racism. The simplistic, idealistic notion that 'we are all the same and we are not speciating' is risible, as is the notion of a 'best genome'. Vives les differences!
I am not specialist in geneticks and most of the technical terminology used in the article I really do not understand. But I have read a lot about evolution and genetics, and do have some background. So, I see nothing wrong in the idea that a group of geographically common part of population has certain characteristics that another geographical group does not have. Specially with traits like health. E.g. it is a known fact that if a group of people will not have a chance to marry a lot outside of their group and will intermarry inside will have much higher proportion of debilitating deseases. Russian Royal family were heavily intermarried and had a lot of gemophiliacs. A lot of Jewish families through centuries living in European schettles (small villages) and having little chance to get out had eventually accumulated bad health problems carried from generation to generation. If you have ever been in Israel and see modern Jewish population you will find that contrary to beleif that Jews are physically weak, in Israel population of young Jewish people is physically more fit than e.g. in a small Ukrainian city of Chernovtczi.
What if we refrained from using words that imply a judgement? To say that something is positive or negative, or deleterious, is a matter of opinion: what can be deleterious for one individual could be very advantageous for another, or the species. At an even greater scale, the extinction of a species (something typically considered negative) can be an opportunity for other species that will enter the same ecological niche. The attribution of judgements to scientific observations reveals more about the author of the comment than about the content of the observation, and often generates disputes that have very little scientific relevance.
Wait a minute. These potential mutations are "considered harmful" because they potentially change the function of the protein? Well, isn't that simply evolution at work? That's equally genetic progress isn't it? I think the problem lies in the scientific interpretation of these results, not in any sociological interpretation.
What about selectable beneficial mutations? ...and what about selection on single pointmutations? ...it implies release of selective constraint on other parts of the genome. ...and if so how did Human Accelerated Regions evolve, for instance the HAR1F gene? ...and if selection can't do that what about the observed conservation of redundant parts of the mice and human genomes? It will appear selection is the phlogiston of evolution theory.
I admit I haven't read the original article, so maybe I'm misreading this news-article. Didn't the author here say that essentially a "non-synonymous" SNP means "different amino acid from chimpanzee" and synonymous SNP means "same amino acid from chimpancee" (i.e. no functional change)? If this were true, then doesn't this imply that the authors' rather small sample of African Americans was found to have a smaller proportion of SNPs which actually had the potential to change the function of a protein away from its chimp-function (47%), compared to the European sample (55%)? I must be completely misunderstanding this, because this would entail that, on the protein level, the African American sample was slightly less different from chimpanzees than the European sample. I'm sure I'm not the only one misunderstanding this, so maybe the author of this newsreport may clarify the respective section to avoid certain racist headlines.