Please explain evolution.

Hi Rookie,Since none of our resident Creationists have seen fit (or are unable) to respond to my challenge inre an operationalized theory, I'd like to draw your attention to my post #154 in this very forum. The post provides a (pretty good, if I do say so myself) non-technical explanation of evolution by natural selection. Your comments/questions are welcome. Maybe that effort will have some value...

Wow Moose! I'm impressed. I'd have never found it. Thanks!Brad: I guess that answers your question...

Hi TB: Although I think our friend Rookie is long gone (there wasn't a reply since January until Brad resurrected the thread), I'd like to address (again, I think) your stand on gene evolution.

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For example, the processes inside cells have factories that translate DNA to proteins or converts glucose to energy. They all involve numerous enzymes (coded for on genes). None of the Darwinian processes I described earlier have ever generated a single new enzyme but our body has tens of thousands of differnet enzyme types for tens fo thousands of different jobs!

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This is a very misleading statement. There is quite ample evidence that novel genes do arise. Obviously, it's easier to detect these genes in organisms which have been fully sequenced (duh). Drosophila melanogaster has probably the most thoroughly investigated genome on the planet. This insect contains at least two completely novel genes. Here's an abstract for one:

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Nature 1998 Dec 10;396(6711):572-5

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Selective sweep of a newly evolved sperm-specific gene in Drosophila.

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Nurminsky DI, Nurminskaya MV, De Aguiar D, Hartl DL.

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Harvard University, Department of Organismic & Evolutionary Biology, Cambridge, Massachusetts 02138, USA.

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The pattern of genetic variation across the genome of Drosophila melanogaster is consistent with the occurrence of frequent 'selective sweeps', in which new favourable mutations become incorporated into the species so quickly that linked alleles can 'hitchhike' and also become fixed. Because of the hitchhiking of linked genes, it is generally difficult to identify the target of any putative selective sweep. Here, however, we identify a new gene in D. melanogaster that codes for a sperm-specific axonemal dynein subunit. The gene has a new testes-specific promoter derived from a protein-coding region in a gene encoding the cell-adhesion protein annexin X (AnnX), and it contains a new protein-coding exon derived from an intron in a gene encoding a cytoplasmic dynein intermediate chain (Cdic). The new transcription unit, designated Sdic (for sperm-specific dynein intermediate chain), has been duplicated about tenfold in a tandem array. Consistent with the selective sweep of this gene, the level of genetic polymorphism near Sdic is unusually low. The discovery of this gene supports other results that point to the rapid molecular evolution of male reproductive functions.

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Now you'll simply say that this represents evolution within a "gene family" (i.e., microevolution), although it appears to me to be indicative that brand new functions CAN arise.That being the case, I'd like to draw your attention to the jingwei gene in the same fly. This is another novel gene. More importantly, it's a chimera - a combination of two completely different gene families.

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In a 1993 issue of Science, Manyuan Long, and CH Langley published their findings of a novel Drosophila gene, located on chromosome 3, that is found in sister species D. teissieri and D. yakuba and thus presumably first appeared in the common ancestor of both. They dubbed this new gene jingwei (jwg). The evidence that they uncovered, especially the lack of introns, suggested that the gene was derived from a retrotransposed mRNA from an alcohol dehydrogenase (adh) gene on chromosome 2. Further results suggested that jwg is not a pseudogene as was first thought, but is rather a functional novel gene, though its exact function is still not clear. The gene not only has specific RNA expression patterns, but has also undergone extensive evolution without suffering from any frameshift or nonsense mutations that are the hallmark of pseudogenes; the evidence strongly suggests that jwg has been under positve Darwinian selection. Not only that, but Long and Langely’s results suggest that selection is playing a role throughout the origin of new genes, rather than being initially relaxed as was previously thought.

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Perhaps the most interesting aspect of jwg is that its gene product is a chimera, meaning that it has function portions that are derived from different ancestral genes (aka gene fusion). The C-terminal portion of jwg was almost certainly derived from the ancestral adh gene via retrotransposition, but that left the origin of the N-terminal exons still unexplained. Did they come from non-coding upstream regions of DNA, or were they derived from parts of non-related functional genes? Further study by Long et al. (1999) demonstrated that the N-terminal regions were the result of duplications of exons from a gene named yellow-emperor (ymp). A follow-up study by Wang et al. (2000) showed that ymp is also a functional gene whose first three exons are the donor for the recruited portion of jwg.

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Here's how it looks graphically: (originally posted by theyeti here)Original references:Wang, W., Zhang, J., Alvarez, C., Llopart, A., and Long, M. 2000. The origin of the Jingwei Gene and the complex modular structure of its parental gene, Yellow Emperor, in D. melanogaster. Mol. Biol. Evol. 17: 1294-1301.Long, M., W. Wang, and J. Zhang, 1999, Origin of New Genes and source for N-terminal `domain of the chimerical gene, jingwei, in Drosophila. Gene. 238: 135-142Some other interesting references for novel genes from the same group:
Long, M. 2001. Evolution of Novel genes. Curr Opin Genet Dev 11:673-680Wang W, Brunet FG, Nevo E, Long M. 2002. Origin of sphinx, a young chimeric RNA gene in Drosophila melanogaster PNAS 99:7, 4448-4453, April 2, 2002Basically, your contention that novel genes can't arise is falsified by the existence of genes generated by mutations and fusion of genes or parts of genes across "families".The second part of your argument, that specific gene families somehow prevent macroevolution, also needs to be addressed. Since this is your claim, for it to be valid you need to show that there are identifiable gene families that are unique to specific taxa. What is the evidence (the specific gene families) that defines, for example, the difference between Aves and Mammalia? Or for that matter, between chordate and invertebrate? Obviously, there are going to be significant genetic differences between these wildly different organisms. In other words, specify which families belong to which taxa. Be careful: if there are genes within a given family that are shared among different organisms, then your contention is falsified. Please be specific.If you are unable to delimit - scientifically - the family differences between taxa, AND show how these provide a barrier, then all you are doing is restating at the genetic level the long-discredited concept of taxic discontinuity. The same falsifications to discontinuity at the species level would apply. (Hint: you're on shaky ground since you already acknowledge that speciation can occur.)[edited to fix attribution][This message has been edited by Quetzal, 08-15-2002]