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  Topic: The Origin of "Information" via natural causes, Refuting a key ID claim (refs, webpages)< Next Oldest | Next Newest >  
theyeti



Posts: 97
Joined: May 2002

(Permalink) Posted: May 30 2002,16:43   

Here's another well studied one:

The jingwei gene in Drosophila.

(quick side note:  you find most of these suckers in well studied organisms like Drosophila whose genome has been sequenced.  The particular significance of this is that we can trace the ancestry of the gene in question by looking at closely related species Drosophila, whose common ancestry is not even doubted by YECs.  Their only recourse here would be to claim that the gene had always existed and that every other species of Drosophila had lost the gene independently.  This would a) be extremely unparsimonious, given that it requires multiple parallelisms with no known non-random mechanism and b) force us to ignore all of the other evidence of recent origin.)  

Onto jingwei:

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.
 
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.









Quote
Fig. 2.—Origin of the three novel proteins, YMP-1, YMP-2, and JGW, as a consequence of exon recombination. E1–E12 represent exons 1–12 of ymp (for the origin of YMP-1 and YMP-2); E1–E3, making up JGW, are the first three exons of ynd (Long and Langley 1993 ), a duplicate copy of ymp. The hatched boxes are the regions encoding protein sequences, with different patterns showing different peptide sequences. The open boxes represent untranslated regions (UTRs) of mRNAs (the open boxes on the left represent 5' UTRs; those on the right represent 3' UTRs)
{from Wang et al, 2000}

That's not the world's best image, but it gets across the general idea of how these new genes evolve.  Notice also that this graphically demonstrates the evolution of the yellow emperor genes as well.  As for jingwei, the basic idea is as follows, and I'd like to get it (and all other such examples) into a fancy colored graphic when possible (if anyone knows of a good program for this, let me know.)

Ald ---> retrotransposition ---> Jingwei Ct portion

YMP --> duplication of first three exons ---> exon shuffling ---> fusion of Jingwei Nt and Ct portions.


Refs:

Long M, Langley CH, Natural selection and the origin of jingwei, a chimeric processed functional gene in Drosophila.  Science 1993 Apr 2;260(5104):91-5
PubMed

Long M, Wang W, Zhang J., Origin of new genes and source for N-terminal domain of the chimerical gene, jingwei, in Drosophila.  Gene 1999 Sep 30;238(1):135-41
full text pdf

Luque T, Marfany G, Gonzalez-Duarte R., Characterization and molecular analysis of Adh retrosequences in species of the Drosophila obscura group.  Mol Biol Evol 1997 Dec;14(12):1316-25
PubMed

Wang W, Zhang J, Alvarez C, Llopart A, Long M., The origin of the Jingwei gene and the complex modular structure of its parental gene, yellow emperor, in Drosophila melanogaster.  Mol Biol Evol 2000 Sep;17(9):1294-301
full text

Edited by theyeti on May 30 2002,16:58

  
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