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Well, well, well. Brian tries to convince us that jumping genes caused favorable mutations within cells, conferring large, superior brains on ape-like ancestors, but it appears that the exact opposite is true:
Evolution of transposons
The evolution of transposons and their effect on genome evolution is currently a dynamic field of study.
Transposons are found in all major branches of life. They may or may not have originated in the last universal common ancestor, or arisen independently multiple times, or perhaps arisen once and then spread to other kingdoms by horizontal gene transfer. While transposons may confer some benefits on their hosts, THEY ARE GENERALLY CONSIDERED TO BE SELFISH DNA PARASITES that live within the genome of cellular organisms. In this way, they are similar to viruses. Viruses and transposons also share features in their genome structure and biochemical abilities, leading to speculation that they share a common ancestor.
Since excessive transposon activity can destroy a genome, many organisms seem to have developed mechanisms to reduce transposition to a manageable level. Bacteria may undergo high rates of gene deletion as part of a mechanism to remove transposons and viruses from their genomes while eukaryotic organisms may have developed the RNA interference (RNAi) mechanism as a way of reducing transposon activity. In the nematode Caenorhabditis elegans, some genes required for RNAi also reduce transposon activity.
Transposons may have been co-opted by the vertebrate immune system as a means of producing antibody diversity. The V(D)J recombination system operates by a mechanism similar to that of transposons.
Evidence exists that transposable elements may act as mutators in bacteria.
-Source, Wiki, under "Transposons." Caps mine.
Hmmm. Generally considered to be selfish DNA parasites, like viruses, and can cause irreparable damage to the genome. Gee, Brian, your vast array of scientific knowledge seems to have collapsed under its own very, very light weight.
Pity, really.--- --- --- --- --- --- --- --- --- Replying to: Note to self: every time John begins a post with "Sir", he's about to lose it.
John, your contradiction within a sentence is what confused me. But as long as we're on the same page now, I'm happy.
To recap: There are a variety of mechanisms by which DNA mutates. These mutations result in random insertions of genetic material, deletions, transpositions and point mutations. Do we all agree on this? Great.
As for your question about the Australopithecus brain vs. the human brain, why don't you find me a primary literature reference on the subject? Just one. Just give me the journal, year and page number. That's it.
Since you find the subject of jumping genes to be absolutely hilarious, here are a couple of references on the subject:
"Evolution of genes and genomes on the Drosophila phylogeny", Nature, 2007, 203.
"Transposable elements and the dynamic somatic genome", Genome Biology, 2007, S5.
Actually, if you want to absolutely die laughing, you can just start sifting through the 21,000 hits that come up when you search for "jumping gene" in PubMed. Seriously, my stomach hurts.
So, that leaves us with, "Where does all that sophisticated code come from?" {no need to yell}
Answer: We both agree (I hope) that DNA is the code that makes us what we are. Furthermore, we both agree that there are a host of mechanisms by which this code can be changed (insertions, deletions, point mutations, transpositions, etc.). The final piece to the puzzle is that, after mutation, an organism will either be better-suited to its environment, or worse-suited. The better-suited live, the others die. This is natural selection. |
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