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Author Topic:   What drove bird evolution?
biochem_geek
Inactive Junior Member


Message 77 of 145 (124842)
07-15-2004 10:15 PM
Reply to: Message 66 by redwolf
07-15-2004 2:19 PM


Re: genetic engineering
quote:
Recent studies in fact indicate that humans appear to have been fabricated using the same techniques which we ourselves are now starting to use in bio-engineering projects, which are anything but natural
I think enough other people have explained that there is nothing "unnatural" about horizontally transferred genes. What they haven't mentioned is there probably aren't any in the human genome. Six months after the paper suggesting hundreds of such genes you get this:
Phylogenetic analyses do not support horizontal gene transfers from bacteria to vertebrates
MICHAEL J. STANHOPE, ANDREI LUPAS, MICHAEL J. ITALIA, KRISTIN K. KORETKE, CRAIG VOLKER & JAMES R. BROWN
Nature 411, 940-944 (21 June 2001)
And as we sequence more and more eukaryote genomes it is becoming clear that the genes that Venter et al claimed only had ortohlogs in bacterial genomes are actually more closely related to eukaryotic sequences.

This message is a reply to:
 Message 66 by redwolf, posted 07-15-2004 2:19 PM redwolf has not replied

  
biochem_geek
Inactive Junior Member


Message 80 of 145 (124875)
07-16-2004 12:00 AM
Reply to: Message 60 by redwolf
07-15-2004 11:54 AM


quote:
http://www.bearfabrique.org/evorants/bioEngineering.html
Amusingly the article you linked do actually gives you a clue about how evolution has probably worked on the vertebrates.
quote:
from the article
The human genome probably does not contain significantly more genes than the fugu fish
Not only are there not very many more genes, they all pretty much the same. If we are being rational that’s 400 million years of evolution and almost exactly the same repertoire of genes yet one is a small, inflatable fish that may be able to make people into zombies and the other is you. The difference between different vertebrates isn’t by and large the presence or lack of genes in their genome but the way in which they are used. Genes are turned on for longer in development, or alternative splicings are used to generate new functionalities on old proteins and probably most importantly new tissue specific regulation of genes arises by the addition of new promoters.
Here is a recently observed example of exactly that
Before you go off on the well that’s just de-evolution of an ancestral type here is an example of a mobile element providing a new promoter to an existing gene and generating new tissue specific regulation in primates
Mobile element insertion can also lead to tissue specific expression of genes. One striking instance of this has recently been revealed. CYP19 is a gene that encodes aromataseP450, an important enzyme in the biosynthesis of estrogen; it is expressed primarily in the gonads and brain of most mammals. In the primates it is also expressed to high levels in the placenta, this expression is driven by a promoter located 100kb upstream of the gene. This alternative promoter has been shown to be the result of a mobile element insertion that happened early in the evolution of primates providing a new way of controlling estrogen levels during pregnancy. The authors of the paper that revealed this fact have described another 15 genes they believe to be alternatively promoted in specific tissue due to a mobile elements insertion proving a new promoter.( Reference )
Now I realize it seems that I’ve got way off topic but I assure you it is not so. Your main argument against the evolution of birds is from personal incredulity, evolving something this different isn’t possible. Other people have eloquently argued that flying could start without the highly intricate systems we see in birds today and how once flying got its start there would be very strong pressure to get better at it and really dominate the new niche. What I’m trying to add is that wings, and lungs and hearts and brains aren’t mutating the genes are. And its becoming more and more clear that very small mutations; moving a splice site, down regulating expression of a gene by adding polyA sequence in an intron or the incorporation of a new promoter from a mobile element is enough to generate major morphological change.
If birds had really been "engineered" surely the creator would start again. To borrow an analogy from Dawkins the first jet engines weren't developed by bashing around prop' driven plane's engines, or just lengthening bolts of panels or cobbling together different parts of the original engine to create new functions. But that is how we, and fugu and birds work.
This message has been edited by biochem_geek, 07-16-2004 05:27 AM

This message is a reply to:
 Message 60 by redwolf, posted 07-15-2004 11:54 AM redwolf has not replied

  
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