Lethean
Posts: 292
Joined: Jan. 2014
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| Quote (REC @ June 26 2014,21:11) | Guess since Sal's Creation-Evolution University has failed, he's back on UD.
His version of scholarship:
| Quote | | A quick google shows hardly any attempt at an evolutionary explanation [of transposons] |
Maybe a more thorough search? Like the 5th result, which deals with the origins and evolution of transposons. Or try PubMed? Shit, did you not have to write a thesis or something for your Masters degree?
| Quote | | I posed the following question on reddit/r/creation: |
Even better. Reddit. Porn, kittens and memes.
| Quote | | Needless to say, I didn’t get any pro-evolutionary explanations for the origin of transposases. |
this subreddit is private
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I wonder why Sal. For fucks sake, you and KF and his crickets are peas in an idiotic-echo-chamber-loving pod. Unlike him, I don't think you lack the intellegence to actually do a literature search. Just the honesty to report what you find. |
Let alone the honesty to search for an answer as if he actually wanted one.
As you point out, Sal's "quick google" rather than an intellectually honest search of the literature, he then opts for asking the private circlejerk of r/creation rather than asking r/science.
r/science is a default subreddit which means the top threads are shown on the homepage to everyone who visits registered or not with nearly 3 million actively subscribed and likely two to three times as many "lurkers" to that specific subreddit in a given month. Hell, without bothering to ask and doing a simple search of r/science gives this result from two years ago from redditor mattc286.
How did transposons first come about?
| Quote | Edit: I should note that transposons are not my specific field of study, but I have a working knowledge of them (I've read papers, attended lectures, and had conversations with people who do work on them).
That's a great question which is the subject of ongoing research. As you've noted, transposons behave similarly to some viruses in many ways. For those who are unfamiliar with transposons, they are transposable elements present in the DNA of many organisms (possibly all), which means they are sections of DNA that are removed by enzymes called "transposases" a locus in a chromosome and insert them somewhere else in the genome of the same cell. This can be in the same chromosome or another chromosome. How they choose their new insertion site is sequence-based for some transposons, and seemingly random for others (though probably at least partially dependent on local chromosomal architecture determined by histone location and post-translational modification and DNA methylation, termed "epigenetic mechanisms"). Some transposons encode for proteins, and some of those encode for their own transposases, and some don't. These transposons have been an invaluable tool for researchers in a lot of fields in biology, including evolution and cancer research. For instance, this guy and his collaborators have developed a forward genetic screen in mice based on a transposon called "Sleeping Beauty" to discover new oncogenes, tumor suppressors, and cancer-modulatory genes.
Like many viruses, transposons can be divided into groups based on their replication mechanism: those that involve an RNA intermediate (retrotransposons and retroviruses) and those that don't (DNA transposons and DNA viruses). Given that a transposon can encode its own transposase (essentially becoming self-replicating), and that they can be engineered to participate in horizontal gene transfer, it's not a far stretch of the imagination that viruses and transposons (and bacterial plasmids) may be evolutionarily linked. The only thing they lack is the ability to leave the cell and infect another cell/organism (horizontal gene transfer). In fact, this is the leading understanding at this time.
The question then becomes: Did viruses arise from transposons-gone-awry or are transposons stripped-down viruses that became integrated into their hosts to such a degree, they gave up on trying to "infect" other cells. The answer is most likely both. Divergence in evolution is always a messy process, and we can find evidence of some transposons that were spread by horizontal gene transfer (aka, they were "viruses"), but the fact that some transposases are encoded in the genome outside of transposons indicates that the virus either left the transposon somewhere else, or that the transposon evolved independently in that species. It's hard to know which came first, the transposon or the virus, because transposons have been around for a long time and are under tremendous selective pressure. Whatever species originally developed the first transposon/virus lived billions of years ago near the beginning of life on Earth, so we can't study it directly. The best we can do is compare DNA sequences and genetic markers in extant transposons and viruses to try to figure out where they came from.
tl;dr: Some transposons and plasmids probably evolved into viruses, and some viruses probably inserted into hosts and turned back into transposons, but we can't rule out that some transposons have evolved independently in different species. |
I'm stating the obvious of course but Sal doesn't want an answer. He doesn't go honestly looking for an answer so he can feel as though technically he's not lying when he claims "darwinists" have no explanation (therefore Yahweh).
I'm not claiming that the post I quoted above from mattc286 is accurate or even answers Sal's question to his satisfaction. I just felt I should share what took me 30 seconds to find by simply following Sal's lead. If I were Sal, and had a lick of intellectual honesty, I would have went digging in the primary literature.
The moniker of "slimy" has been earned. What a sad sad pretender.
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"So I'm a pretty unusual guy and it's not stupidity that has gotten me where I am. It's brilliance."
"My brain is one of the very few independent thinking brains that you've ever met. And that's a thing of wonder to you and since you don't understand it you criticize it."
~Dave Hawkins~
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