From: alexandru_mg3
Message: 65379
Date: 2009-11-07
--- In cybalist@yahoogroups.com, "alexandru_mg3" <alexandru_mg3@...> wrote:
>
>
> I. FOXP2 is a transcription factor - affecting the expression of many genes
> ==============================================================
> "The key point, that all the popular reports missed, is that FOXP2 is a transcription factor - in other words it has the potential to affect the expression of an unknown, but potentially large number of other genes."
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>
> II. FOXP2 -> 75 Million years - ONE MUTATION versus 6 MILLION years - 2 MUTATIONS
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> "The major splice form of the protein encoded by the gene (it has a pair of alternatively spliced exons) is 715 amino acids long and the protein is identical with no differences whatsoever in chimpanzee, gorilla and rhesus monkey.
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> The mouse FOXP2 differs in just one amino acid from these three species.
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> However, HUMAN FOXP2 differs from gorilla, chimp and rhesus macaque in TWO further amino acids (and thus differs from mouse in three amino acids out of 715).
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> So, in 75 million years since the divergence of mouse and chimpanzee lineages ONLY ONE change has occurred in FOXP2, (and that equates to 150 million years of evolution as we don't know whether the mutation occurred in the mouse or the primate lineage)
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> whilst in the 6 million years since the divergence of man and chimpanzee lineages TWO changes have occurred in the human lineage.
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> Furthermore the ONE change between chimp and mouse is predicted to be functionally unimportant,
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> and BOTH changes that have occurred in the human lineage occur on the same exon of the gene and at least one of them is predicted to be functionally important (an aspargine to serine change that provides a target site for phosphorylation which is a process that has been shown to mediate transcription in forkhead transcription factors). "
> "
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>
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> III. SELECTIVE SWEEP
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> Next, Enard et al searched for evidence of a selective sweep in the region of the FOXP2 gene. A selective sweep occurs when a particularly beneficial mutation spreads rapidly through a population. THE SELECTIVE SWEEP ELIMINATES NOT JUST ALTERNATIVE ALLLELES OF THE GENE IN QUESTION BUTA ALSO REDUCES THE POLYMORPHISM OF OTHER GENES THAT ARE PHYSUCXALLY CLOSE (LINKED) ON THE CHROMOZOME. Enard et al found strong evidence of this both in introns within FOXP2 and in recombining loci. So they suggest that the selective sweep was caused by one or both of the mutations in humans, and then they go on to speculate that this change has been critical in the evolution of human speech, perhaps by enabling fine oro-facial movements essential to speech
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> IV. The mutations in the FOXP2 in the human lineage possible occured only recently between 10,000 and 100,000 years ago
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> Finally, by looking at silent polymorphisms in the gene, Enard et al estimate that the mutations in the FOXP2 in the human lineage occurred between 10,000 and 100,000 years ago and speculate that the mutations have been critical for the development of human speech as we understand it and also critical for the development of fully human society and cognition
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> url:
> http://www.evolutionpages.com/FOXP2_language.htm
>