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Genetic Surprise Confirms Neglected 70-Year-Old Evolutionary Theory
University of Rochester ^ | 08 September 2006 | Staff (press release)

Posted on 09/07/2006 2:20:41 PM PDT by PatrickHenry

Mobile Genes Found to Pressure Species Formation.

Biologists at the University of Rochester have discovered that an old and relatively unpopular theory about how a single species can split in two turns out to be accurate after all, and acting in nature.

The finding, reported in today's issue of Science, reveals that scientists must reassess the processes involved in the origin of species. The beginnings of speciation, suggests the paper, can be triggered by genes that change their locations in a genome.

"In the 1930s there was speculation that parts of chromosomes that switch from one location to another might cause a species to split into two different species," says John Paul Masly, lead author of the paper and doctoral student at the University of Rochester. "Showing that it was more than an academic idea was difficult, and required a bit of luck. Other genetic causes of speciation are clearly documented in nature, and it wasn't until we had the ability to sequence whole genomes that we could even attempt to investigate the question."

Curiously, the hypothesis nearly died twice.

Theodosius Dobzhansky, a well-known evolutionary geneticist, studied fruit flies in the infant days of genetic research in 1930. He mapped out how it might be possible for sections of chromosomes to relocate themselves in a genome. Those mobile sections can cause sterility in inter-species hybrids, which can act as a speciation pressure.

In theory, the idea was sound, but scientists long debated whether it actually happened in nature. Eventually a competing theory involving the gradual accumulation of mutations was shown to occur in nature so often that geneticists largely dismissed the moving gene hypothesis.

"We knew going into this that it was a risky experiment," says Masly. "But we hoped we could pull it off."

Over the span of the six-year project, the prospects of bolstering the controversial evolutionary idea looked increasingly bleak.

Masly brought together two species of fruit fly—the workhorses of the genetics world—to see what genes were active when they were crossbred. One species, Drosophila melanogaster, had its genome already sequenced, making that part of the job much easier. The second species, Drosophila simulans, was still in the process of being sequenced, which meant much of the work had to be done by hand by Masly and his collaborators.

Masly knew that chromosome #4 on melanogaster held a gene that was somehow very important for fertility—information found earlier by Rochester biologist H. Allen Orr. Crossbreeding the flies proved tricky because a few million years of evolution separated the species, but after a few nudges the flies produced what Masly was looking for—a sterile male.

This is when Dobzhansky's 70-year-old hypothesis nearly died for good.

The reigning theory of speciation says that the genes causing hybrid sterility must have diverged slowly by normal evolutionary changes. To determine if this was true, Masly had only to look at chromosome #4 and find the gene on it that caused the hybrid sterility.

But there was no gene there.

"There was a great, 'Oh no,' moment," says Masly. "I'd been working on this for six years and it was starting to look like it was all for nothing. Something was all wrong. We couldn't find the gene and we were this close to giving up on the whole project."

But once again, insights from the past came into play. Masly and Orr, Masly's advisor and professor of biology at the University of Rochester, were talking one day when Orr suddenly recalled an off-hand comment from a scientist named Hermann J. Muller in a paper 60 years earlier. Muller speculated that perhaps since the sterility in the flies is so recessive—meaning it's almost completely non-functional—perhaps the gene in question has jumped clear off the chromosome.

"It had never occurred to us that the gene might have moved right off chromosome #4 in simulans," says Masly. As the simulans' genome was newly sequenced, Masly called a colleague, geneticist Corbin D. Jones, a co-author of the paper and Rochester graduate, who was studying the simulans genome.

Over the phone one day in the lab, Jones told Masly what his analysis turned up.

"You're not going to believe this, but you're right," said Jones. "It's not on the fourth chromosome. It's on the third."

"That was really exciting," says Masly. "It was completely unexpected and it made the cause of this hybrid's sterility very simple; the gene's on number four in one species and on number three in the other, so when you mate the two, every now and then you'll get a male with a combination that includes no gene at all. These guys are sterile because they completely lack a gene that's necessary for fertility."

The gene, called JYAlpha, is one of the same genes that is essential for sperm motility in the flies, as well as in humans and other mammals.

Masly's work shows a back door through which speciation can start. If the right genes jump around in the genome, a population can begin creating individuals that can't successfully mate with the general population. If other speciation pressures, like geographic isolation, are added to the mix, the pressure may be enough to split one species into two new species.

When asked if JYAlpha may be responsible for melanogaster and simulans' initial split a few million years ago, Masly replied, "That's lost to history."

Fortunately, the theory isn't.

This research was funded by the National Science Foundation, the Canadian Institutes of Health Research, and the National Institutes of Health.


TOPICS: Culture/Society; Philosophy
KEYWORDS: creationofsterility; crevolist; onetrickpony
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Everybody be nice.
1 posted on 09/07/2006 2:20:42 PM PDT by PatrickHenry
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To: PatrickHenry

Okley Dokely.


2 posted on 09/07/2006 2:21:35 PM PDT by Junior (Identical fecal matter, alternate diurnal period)
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To: VadeRetro; Junior; longshadow; RadioAstronomer; Doctor Stochastic; js1138; Shryke; RightWhale; ...
Evolution Ping

The List-O-Links
A conservative, pro-evolution science list, now with over 390 names.
See the list's explanation, then FReepmail to be added or dropped.
To assist beginners: But it's "just a theory", Evo-Troll's Toolkit,
and How to argue against a scientific theory.

3 posted on 09/07/2006 2:22:11 PM PDT by PatrickHenry (Where are the anachronistic fossils? Where are the moderate creationists?)
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To: PatrickHenry

Does this say that the gene is actually in two parts and each part is on a different chromosome but that if either part is present the gene manifests?


4 posted on 09/07/2006 2:25:16 PM PDT by RightWhale (Repeal the law of the excluded middle)
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To: PatrickHenry

Interesting. I wonder how often this happens?


5 posted on 09/07/2006 2:26:42 PM PDT by Zeroisanumber (Quis custodiet ipsos custodes?)
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To: PatrickHenry
Hmmm. Gosh, I'm not a PhD, but this supports what I've said in the past about "other reasons for mutation". I wonder if the same folks that called me an idiot for having such a hypothesis will protest these findings.
6 posted on 09/07/2006 2:29:17 PM PDT by SampleMan
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To: PatrickHenry

But, but ....it's some of the best discussion on FR because those pesky evolutionary people get so angry .......;-)


7 posted on 09/07/2006 2:30:03 PM PDT by svcw
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To: PatrickHenry

BTTT


8 posted on 09/07/2006 2:33:10 PM PDT by oxcart (Journalism [Sic])
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To: PatrickHenry

That's pretty cool! Good post.


9 posted on 09/07/2006 2:38:57 PM PDT by Coyoteman (Evolution is real, deal with it!)
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To: svcw
But, but ....it's some of the best discussion on FR because those pesky evolutionary people get so angry .......;-)

Hey, you started it by claiming that they might not be the only people in the world who know everything.....

10 posted on 09/07/2006 2:41:30 PM PDT by Onelifetogive (* Sarcasm tag ALWAYS required. For some Freepers, sarcasm can NEVER be obvious enough.)
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To: PatrickHenry
I luv this part..."perhaps the gene in question has jumped clear off the chromosome"

Fly mite..."That does it - this fly is starting to act like a woodpecker and I can't sleep. I'm out of here!"

11 posted on 09/07/2006 2:42:43 PM PDT by patriot_wes (Infant baptism - the foundation of an unbelieving and unsaved church.....)
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To: RightWhale
Does this say that the gene is actually in two parts and each part is on a different chromosome but that if either part is present the gene manifests?

I read it to say that the gene is required and is either on C3 or C4. If a pair of mis-matched flies breed it's possible that the gene will not be on either chromosome in the offspring so those offspring will be sterile.
12 posted on 09/07/2006 2:48:02 PM PDT by Filo (Darwin was right!)
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To: SampleMan
Hmmm. Gosh, I'm not a PhD, but this supports what I've said in the past about "other reasons for mutation".

Moving genes, and many even more drastic chromosomal mutations, have been known, and included as "mutations" for many decades. I have no idea what you could be talking about. (I don't recall your earlier posts off the top of my head.) There are some antievolutionists here who pretend as if evolutionists only "believe" in simple point mutations, but that's just a straw man.

13 posted on 09/07/2006 2:49:33 PM PDT by Stultis
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To: Filo

Possible. So the gene would not necessarily be on both, but could be on neither. In any case the gene is complete in itself on either chromosome.


14 posted on 09/07/2006 2:51:00 PM PDT by RightWhale (Repeal the law of the excluded middle)
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To: Stultis

Some of those straw men are awful fancy.


15 posted on 09/07/2006 3:01:48 PM PDT by b_sharp (Objectivity? Objectivity? We don't need no stinkin' objectivity.)
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To: PatrickHenry
I don't know how you do it - day in/day out, you're out there putting up the good fight. Personally, I find it all so very tiresome. If it isn't obvious to all, within 50-100 years, scientists & industry will be utilizing genetic engineering to address practically every issue confronting humanity. And it won't be mundane speciation.

Example: how/why did our senses evolve? What is their physical manifestation? What if the basic drivers could be replicated without the actual physical sensation? For instance, why do we enjoy music? Why does certain food taste so good?

The day is coming quite soon when we will have the ability to directly manipulate these sensations via artificial means. Why devote millions of acres to growing foodstuffs when crops can be genetically altered to produce the most nutrients/calories & combine this with genetically altered humans so that they think they are eating steak?

Ditto music; who needs sound when the same response mechanism can be artificially triggered? Science isn't progessing at a linear or geometric rate; rather, it's practically exponential.

These are exciting times - wasting it on debates with people who you would normally never even know existed, as they operate completely out of your sphere, is a futile excercise.

16 posted on 09/07/2006 3:02:50 PM PDT by Chuck Dent
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To: Chuck Dent
In a way, your future scenario confirms the article's premise - we are evolving into two different species already. ;)

I'll take it further - in less than five hundred years further developments in quantum physics may help us understand consciousness well enough to evolve beyond the need to occupy a physical body. We'll be able to send our consciousness anywhere in the Universe, with just a thought. And some of us on FR today will still be alive to experience that transformation.

17 posted on 09/07/2006 3:10:28 PM PDT by Mr. Jeeves ("When the government is invasive, the people are wanting." -- Tao Te Ching)
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To: Stultis; Badray

IIRC, this is technically call a "Trans-location"....not only can genes be eliminated, but sometimes they can be duplicated...with disastrous results. When genes get doubled up, they and can mimick other diseases like "Trisomy-21"....Downs syndrome.

Interesting stuff ping to Badray.

Fountain of worthless knowledge /OFF.......LOL.


18 posted on 09/07/2006 3:17:32 PM PDT by Conservative Goddess (Politiae legibus, non leges politiis, adaptandae)
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To: Stultis

Now why does this stuff stick with me......but I can't tell you what I had for lunch? LOL

http://en.wikipedia.org/wiki/Chromosomal_translocation


19 posted on 09/07/2006 3:22:07 PM PDT by Conservative Goddess (Politiae legibus, non leges politiis, adaptandae)
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To: Junior
Image Hosted by ImageShack.us Hi-diddly ho, neighborino!
20 posted on 09/07/2006 3:37:28 PM PDT by Boxen (:3)
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