tag:blogger.com,1999:blog-37148773.post3603879767650643207..comments2024-03-27T14:50:47.345-04:00Comments on <center>Sandwalk</center>: Laurence Hurst Discusses Junk DNALarry Moranhttp://www.blogger.com/profile/05756598746605455848noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-37148773.post-42648139314793079872013-06-25T15:41:56.223-04:002013-06-25T15:41:56.223-04:00The creationists on UD are in a true conondrum her...The creationists on UD are in a true conondrum here, do they side with an actual true "Darwinist"(read, adaptationist) and say he has it right, or reject both junk-DNA and the adaptationist arguments against it? Mikkel Rumraket Rasmussenhttps://www.blogger.com/profile/07670550711237457368noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-86592146749853822702013-06-25T15:24:55.918-04:002013-06-25T15:24:55.918-04:00Typo - that should be "Zuckerkandl". I s...Typo - that should be "Zuckerkandl". I should also point out that they did mention (but chose not to emphasize) genetic drift in their paper.<br />Konradhttps://www.blogger.com/profile/06867375994008638278noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-65117441124558772412013-06-25T15:20:43.053-04:002013-06-25T15:20:43.053-04:00"the existence of an approximate molecular cl..."the existence of an approximate molecular clock means that most synonymous mutations and amino acid substitutions are fixed by random genetic drift"<br /><br />Interestingly, this is not at all what Zuckerkanl and Pauling had in mind when they introduced the molecular clock hypothesis in 1965 ( http://rana.lbl.gov/290/papers/zuckerkandl_pauling.pdf ). Instead, they seem to have been assuming that most observed changes were fixed under positive selection, but made a distinction between the evolution of sequences which are far from optimality (which they did not expect to be clock-like, e.g. a new function for a particular gene might appear in a particular lineage, causing accelerated evolution of that gene in that lineage), and that of sequences which are nearly optimal but tracking a gradually changing fitness landscape (which they did expect to be clock-like, on the assumption that such fitness landscape changes happen more or less continuously in all lineages).<br /><br />"Hurst has published evidence that some of these seemingly neutral mutations affect function"<br /><br />Independently of Hurst's work, the evidence from model-based approaches ( e.g. http://www.ncbi.nlm.nih.gov/pubmed/16107593 and http://www.virologyj.com/content/5/1/160 ) clearly shows that site-to-site variation of synonymous substitution rates is pervasive. The scale of variation is much too fine to be explained by mutation rate variation - instead, this is indicative of weak purifying selection. Hurst has described several plausible mechanisms for this.Konradhttps://www.blogger.com/profile/06867375994008638278noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-2279119620416095902013-06-25T06:22:36.164-04:002013-06-25T06:22:36.164-04:00I apologize for accidentally closing comments on t...I apologize for accidentally closing comments on this post. Commenting is now allowed.Larry Moranhttps://www.blogger.com/profile/05756598746605455848noreply@blogger.com