Daniel Smith
Posts: 970
Joined: Sep. 2007
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| Quote (mitschlag @ Oct. 13 2007,18:22) | | Quote (Daniel Smith @ Oct. 13 2007,13:53) | | Quote (mitschlag @ Oct. 10 2007,12:47) | | Quote (Daniel Smith @ Oct. 10 2007,02:30) | | The results that would falsify my hypothesis would be if the coding sequences showed evolutionary constraint while the non-coding sequences didn't. |
There's a fair amount of evidence showing that (contrary to expectation) non-coding sequences have fewer base changes than coding sequences, see, for example:
http://www.biomedcentral.com/1471-2148/7/66
| Quote | The primary result is that the mean rate of intergenic nucleotide substitution is two-thirds that of the synonymous coding data, with an absolute rate estimated to be 1.05 × 10-8 substitutions per site per year. This result holds with alternative nucleotide models (see Methods), and thus does not appear to be solely an issue of estimation procedures.
Slower rates in non-coding regions relative to synonymous sites are becoming a surprisingly frequent observation. For example, a recent study of Drosophila demonstrated that non-coding DNA evolves considerably slower than synonymous sites in terms of both divergence between species and polymorphism within species [16]. By comparing studies, one can also make the case that pseudogenes [32,33] and introns [34,35] evolve more slowly than synonymous sites in apes and other mammals [13,36-38]. Studies of mammalian intergenic regions have also found slower rates than synonymous sites [35,39,40]. Although most of these studies encompass only a handful of genes, an overall picture of relatively slow non-coding rates is emerging. |
What do you make of that? |
If this is true, then it would be a confirmation of my hypothesis with better than expected results. |
It's true, all right, but it doesn't confirm your hypothesis.
To learn why, read the cited paper. Hint: TE=transposable element.
(Sorry that I won't be able to participate in this discussion for the next two weeks due to travel in arcane regions. In the meantime, I want to commend DS for his courteous and patient responses to the many challenges that have been addressed to him.) |
I read the cited paper. It was very interesting - a bit over my head - but interesting nonetheless.
Your suggestion to read up on transposable elements was very fruitful as well as now these have piqued my interest. I, of course, don't believe these to be randomly generated or to be degenerate copies of working genes. I think they are more likely functional switches for some as yet undefined purpose. I'm going to read more about them.
Oh and thanks for the commendation. I appreciate a good civil discussion. Unfortunately, when things get hostile, I have a tendency to get my guard up and push back a little harder than I have the right to. Thanks for putting up with that as well.
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"If we all worked on the assumption that what is accepted as true is really true, there would be little hope of advance." Orville Wright
"The presence or absence of a creative super-intelligence is unequivocally a scientific question." Richard Dawkins
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