Monday, July 23, 2007

A de novo-'Out of Nowhere'-Gene

At uncommondescent, PaV find it interesting how "Darwinists" explain things. He is referring to a gene - hydra - found in various species of the fruit fly Drosophila that appears to not to be related to other genes in any known genome. What is interesting, according to PaV, is that since gradual accumlation of mutations in a duplicated gene is an unlikely source for this gene, the scientists that described it actually propose an alternative explanation for how this gene might have ended up in the flies genomes. The explanation proposed is that a virus which carried a transposon that inserted itself into an ancestral fly genome. PaV says:
While that’s, hypothetically possible, right now there’s no way of proving that since, per the author, “You cannot find any related genes in the fly genome or any species’ genome, and that is what is unique.” (my emphasis) Is this simply grasping at straws? Or, are they onto something? I guess time will tell.
Being that I have done some research into bacterial horizontal gene transfer, especially regarding integrons and gene cassettes, I don't find the researchers proposed explanation particularly far-fetched. To explain why, I must first give a quick explanation of what integrons/gene cassettes are. They all consist of a gene that codes for a protein known as an integrase. Near this gene is an attachment site where the integrase can either insert of excise something known as gene cassettes. Gene cassettes, in turn, consist of a recombination site (recognised by the integrase) and most often an ORF that is typically some hundreds of bases long. ORFs found in gene cassettes often carry adaptive traits such as antibiotic resistance but more to the point it is fairly common for them to not have any known homologues - just as in the case of hydra. So when the researchers propose that hydra was transferred from another organism, I don't think thay are grasping for straws at all. I'm more surprised that such genes are not found more often. Granted, integrons/gene cassettes are only known to exist in prokaryotes, but it not exactly unheard of that foreign DNA can insert itself into eukaryotes either (think HIV and herpes virus).

What I find interesting is that PaV finds it interesting how "Darwinists"explain things. Proposing a plausible explanation is simply good science and shouldn't be sneered at.


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