tag:blogger.com,1999:blog-37148773.post2578527901420294307..comments2024-03-27T14:50:47.345-04:00Comments on <center>Sandwalk</center>: The function wars are overLarry Moranhttp://www.blogger.com/profile/05756598746605455848noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-37148773.post-6547658667220146642023-01-12T07:41:56.711-05:002023-01-12T07:41:56.711-05:00Hi Larry Moran,
in my capacity as the bulldog of ...Hi Larry Moran,<br /><br />in my capacity as the bulldog of modern synthesis, a few minor science theory references:<br /><br />i. <i>“Functional DNA is DNA that is currently under purifying selection”</i><br /><br />This <i>“definition of the conservation function”</i> uses circular logic. Another circular argument is contained in the word <i>“currently”</i>. By the way, the real “maintenance function” is called adaptation.<br /><br />ii. As a systems biology approach, functional genomics looks at the interaction of genes and proteins (structure, function, regulation) at the level of the entire genome. Against the background of functional genomics, junk DNA would then have the function of having no function [<i>sic!</i>]. Functions do not know evolution; they are present or not. If the adaptive properties depicted in the structure of a sequence are indispensable, then all other sequence segments are play money of evolution: mutation catcher AKA potential preadaptation.<br /><br />iii. <i>“Some people might say, “Well the function of this gene is in the development of cancer,” but they don’t really mean that natural selection put it there so that it would cause cancer.”</i><br /><br />Ford Doolittle is much closer to me here than you are. Nevertheless: It is indeed not impossible that natural selection could prefer the development of cancer. If this were otherwise, there would be neither p53, sickle cell disease, asexual reproduction via dieback in <i>Volvox</i>, nor infectious cancer in Tasmanian devils. Of course, natural selection also makes junk!<br /><br />iv. <i>“That kicked off the most intense years of the function wars when scientists and philosophers combined to work out a reasonable definition of function based on evolutionary principles and, at the same time, demonstrate the uselessness of a definition based entirely on some sort of activity that may or may not be indicative of real function.”</i><br /><br />Formally, functions are left-total. For example, it can be said that a bird's wing serves to fly. This does not mean that the wings of flightless birds have the function of being able to fly. This is vivid proof that functions - of whatever kind - cannot be based on evolutionary principles. Bird wings, however, have evolved by adaptive means.<br /><br /><br /><br /><br />Cheers,<br /><br />LamarckLamarckhttps://www.blogger.com/profile/16658282502276785072noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-25570088697443321182023-01-03T10:47:23.865-05:002023-01-03T10:47:23.865-05:00jb asks, "What am I missing"
You're...jb asks, "What am I missing"<br /><br />You're missing the point. When I say that functional DNA is maintained by purifying selection I'm speaking in "big picture" language. I never meant to imply that every single nucleotide in a functional region is resistant to change. I thought that was obvious but I'm glad of the opportunity to make it clear. <br /><br />Conserved regions of DNA are not absolutely conserved. They are simply more conserved than regions that evolve at the neutral rate. There are many nucleotides within conserved regions that can change due to mutation and fixation by random genetic drift. That's why homologous genes in distant species are only 70% similar or 30% similar and not 100% similar.<br /><br />In cases where it's the size of the region that's important and not the sequence, it doesn't mean that the exact size is conserved. There can be considerable variation as long as a minimum, or maximum, size of spacer DNA is maintained. <br /><br />HTH HANDLarry Moranhttps://www.blogger.com/profile/05756598746605455848noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-75136599469221557542023-01-03T09:41:25.761-05:002023-01-03T09:41:25.761-05:00The definition, "Functional DNA is DNA that i...The definition, "Functional DNA is DNA that is currently under purifying selection - it is being maintained by natural selection" seems very adaptationist. Surely you're not suggesting neutral evolution only affects non-functional DNA. <br /><br />What am I missing?jbhttps://www.blogger.com/profile/10835283301887184369noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-5395552993821301812023-01-01T17:48:46.439-05:002023-01-01T17:48:46.439-05:00Unfortunately, there will still be articles writte...Unfortunately, there will still be articles written about how junk DNA has been debunked a decade from now...Georgi Marinovhttps://www.blogger.com/profile/12226357993389417752noreply@blogger.com