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Author Topic:   Evolution Requires Reduction in Genetic Diversity
caffeine
Member (Idle past 1134 days)
Posts: 1800
From: Prague, Czech Republic
Joined: 10-22-2008


Message 517 of 1034 (758102)
05-19-2015 1:22 PM
Reply to: Message 516 by herebedragons
05-19-2015 12:13 PM


Selection on non-coding DNA
I just think it is too generalized and unspecific and gives a false impression of what it represents. Non-coding DNA is better. Reference to more specific types of non-coding sequences is even better.
In the context of this discussion, there is not 95% of the human genome that is "dead genes." That is one example of how the term "junk DNA" is misleading.
Worth pointing out in this context is that there is now considerable evidence of selection on non-coding DNA. As an example, see Positive and Negative Selection on non-coding DNA in Drosophilia simulans, chosen because it was one of the first relevant papers I found that was available as a free pdf rather than for any particular significance. Some non-coding DNA appears to be of adaptive signifcance, at least in fruit flies and humans, where this has been investigated in most depth.
Edited by caffeine, : No reason given.
Edited by caffeine, : tags

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caffeine
Member (Idle past 1134 days)
Posts: 1800
From: Prague, Czech Republic
Joined: 10-22-2008


Message 652 of 1034 (758585)
05-28-2015 4:15 PM
Reply to: Message 630 by Taq
05-26-2015 4:34 PM


Re: Moderator Introduced Definitions
The descriptor "junk" gives us additional information, that the stretch of DNA in question shows no signs of positive or negative selection.
But the problem is that it is not clear any such thing exists. I linked earlier to [/url=http://genomics.princeton.edu/...files/Haddrill_etal2008.pdf]a study[/url] that tested neutrality of non-coding DNA in two species of Drosophila. Their conclusion (emphasis mine):
quote:
In summary, we have examined patterns of evolution at several classes of noncoding DNA in D. simulans and find that all noncoding DNA is subject to the action of negative selection, indicated by low levels of polymorphism and divergence and a skew in the frequency spectrum toward rare variants.
I lack the expertise to assess the maths behind their claims, but if they're right then we can see detectable evidence of negative selection against changes in non-coding DNA. They also claim evidence of positive selection in untranslated DNA in Drosophila simuans.

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 Message 630 by Taq, posted 05-26-2015 4:34 PM Taq has replied

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