Skip to comments.Genetic Surprise Confirms Neglected 70-Year-Old Evolutionary Theory
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 flythe workhorses of the genetics worldto 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 fertilityinformation 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 fora 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 recessivemeaning it's almost completely non-functionalperhaps 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.
Nahhhhh, yer still a idjit...
(And the tin men have a heart.>
My son had APL leukemia, which as far as I know, always involves a complete translocation between chromosome #15, and #17...these two chromosomes switch places...this transloction is one of the criteria, used to categorize anyones particular type of leukemia...my son also had a monosomy-trisomy switch between chromosome #7 and #8...dont remember exactly which chromosome did what, but the arm of one chromosome, split off, and joined itself to the chromosome next to it...this particular transloctions is seen in many AML leukemias...
The more interesting thing to me was that this genetic profile done on my son was done at diagnosis...once he was in remission, a follow up genetic study was done, and that genetic study revealed no translocations of any sort...his genetic study, while in remission showed a normal set of genetics...
However, when he relapsed a third genetic study was done, which again show the same two genetic translocations that my son had at diagnosis...
My question was, what does this mean?...did the translocations cause the disease or does the disease cause the translocations?...translocations are seen only when the disease is present and active...when the disease is in remission, no translocations are found..
We don't do it for them. The entire mission of these science threads -- aside from the unexpected delight of having met scores of bright, talented, and conservative scientists and engineers working in academia and industry, plus a huge number of others who are highly educated and appreciative of science -- is to demonstrate to the lurkers (there are 669 views of this thread and only 23 posts) that there are conservatives, loads of them, who aren't anti-science idiots.
Thanks for the ping.
Thank you for sharing that information. That is VERY interesting indeed. I'm a lawyer/accountant, not a geneticist (But I did stay at a Holiday Inn Express lastnight)....so I really don't know which came first, the translocation or the disease....but it is a VERY interesting question. If they are only present when the disease is active, that would suggest to me that the translocations are a manifestation of an underlying disease, not the cause....but again, I'm NOT a geneticist.
May God heal and bless your son...and you too.
You have Freepmail...
Why sure. Isn't idiot a species? :-)
I thought this evolution thing had been settled. Why are they still searching for proof?
Maybe those people don't exist. Perhaps you are arguing with a biogenetic computer. Perhaps you are, too.
PH, your post #24, is most excellent..glad that you posted those numbers...puts to rest, the notion that a lot of scoffers have tried to spread around, that there are very few lurkers..indeed if your numbers are any indication, there are volumes of lurkers...
Science does not deal in "proof" but in evidence.
Who knows, some new evidence might disprove the current theory of evolution. Do you want scientists to stop looking?
Or, as it has for the last 150 years, new evidence might help to support and fill out the theory.
Here are some definitions (from a google search, with additions from this thread):
Theory: a well-substantiated explanation of some aspect of the natural world; an organized system of accepted knowledge that applies in a variety of circumstances to explain a specific set of phenomena; "theories can incorporate facts and laws and tested hypotheses." Addendum: "Theories do not grow up to be laws. Theories explain laws." (Courtesy of VadeRetro.)
Theory: A scientifically testable general principle or body of principles offered to explain observed phenomena. In scientific usage, a theory is distinct from a hypothesis (or conjecture) that is proposed to explain previously observed phenomena. For a hypothesis to rise to the level of theory, it must predict the existence of new phenomena that are subsequently observed. A theory can be overturned if new phenomena are observed that directly contradict the theory. [Source]
When a scientific theory has a long history of being supported by verifiable evidence, it is appropriate to speak about "acceptance" of (not "belief" in) the theory; or we can say that we have "confidence" (not "faith") in the theory. It is the dependence on verifiable data and the capability of testing that distinguish scientific theories from matters of faith.
Hypothesis: a tentative theory about the natural world; a concept that is not yet verified but that if true would explain certain facts or phenomena; "a scientific hypothesis that survives experimental testing becomes a scientific theory"; "he proposed a fresh theory of alkalis that later was accepted in chemical practices."
Proof: Except for math and geometry, there is little that is actually proved. Even well-established scientific theories can't be conclusively proved, because--at least in principle--a counter-example might be discovered. Scientific theories are always accepted provisionally, and are regarded as reliable only because they are supported (not proved) by the verifiable facts they purport to explain and by the predictions which they successfully make. All scientific theories are subject to revision (or even rejection) if new data are discovered which necessitates this.
Law: a generalization that describes recurring facts or events in nature; "the laws of thermodynamics."
Model: a simplified representation designed to illuminate complex processes; a hypothetical description of a complex entity or process; a physical or mathematical representation of a process that can be used to predict some aspect of the process; a representation such that knowledge concerning the model offers insight about the entity modelled.
Speculation: a hypothesis that has been formed by speculating or conjecturing (usually with little hard evidence). When a scientist speculates he is drawing on experience, patterns and somewhat unrelated things that are known or appear to be likely. This becomes a very informed guess.
Guess: an opinion or estimate based on incomplete evidence, or on little or no information.
Assumption: premise: a statement that is assumed to be true and from which a conclusion can be drawn; "on the assumption that he has been injured we can infer that he will not to play"
Impression: a vague or subjective idea in which some confidence is placed; "his impression of her was favorable"; "what are your feelings about the crisis?"; "it strengthened my belief in his sincerity"; "I had a feeling that she was lying."
Opinion: a personal belief or judgment that is not founded on proof or certainty.
Observation: any information collected with the senses.
Data: Individual measurements; facts, figures, pieces of information, statistics, either historical or derived by calculation, experimentation, surveys, etc.; evidence from which conclusions can be inferred.
Fact: when an observation is confirmed repeatedly and by many independent and competent observers, it can become a fact.
Truth: This is a word best avoided entirely in physics [and science] except when placed in quotes, or with careful qualification. Its colloquial use has so many shades of meaning from it seems to be correct to the absolute truths claimed by religion, that its use causes nothing but misunderstanding. Someone once said "Science seeks proximate (approximate) truths." Others speak of provisional or tentative truths. Certainly science claims no final or absolute truths. Source.
Science: a method of learning about the world by applying the principles of the scientific method, which includes making empirical observations, proposing hypotheses to explain those observations, and testing those hypotheses in valid and reliable ways; also refers to the organized body of knowledge that results from scientific study.
Religion: Theistic: 1. the belief in a superhuman controlling power, esp. in a personal God or gods entitled to obedience and worship. 2. the expression of this in worship. 3. a particular system of faith and worship.
Religion: Non-Theistic: The word religion has many definitions, all of which can embrace sacred lore and wisdom and knowledge of God or gods, souls and spirits. Religion deals with the spirit in relation to itself, the universe and other life. Essentially, religion is belief in spiritual beings. As it relates to the world, religion is a system of beliefs and practices by means of which a group of people struggles with the ultimate problems of human life.
Belief: any cognitive content (perception) held as true; religious faith.
Faith: the belief in something for which there is no material evidence or empirical proof; acceptance of ideals, beliefs, etc., which are not necessarily demonstrable through experimentation or observation. A strong belief in a supernatural power or powers that control human destiny.
Dogma: a religious doctrine that is proclaimed as true without evidence.
Some good definitions, as used in physics, can be found: Here.
Based on these, evolution is a theory. CS and ID are beliefs.
[Last revised 8/27/06]
Do you want scientists to stop looking?
Yes!! No telling what they might find!!
It's possible that there is an underlying cause for both the disease and the translocations. Possible both are caused by copying errors in the cells making the blood. (I'm not a geneticist, but I did teach genetics at one university.)
As of now, there are 36 posts and 860 views. Every now and then I get a freepmail from a lurker. They appreciate what we do here, but don't want to get involved in these threads because of all the toxic, venomous science-deniers, who manage to embarrass both conservatism and religion at the same time.
Wow your update figures are even more impressive...I do know there are many, many lurkers out there, who dont want to get involved, because these threads really are very often quite toxic as you say...but you have proved that the lurkers do exist, they exist in big numbers, and its important that they get the scientific facts....thanks to the fine scientific minds here at FR, they get just that..
Where we will be in 50 years is far beyond exciting. So long as we survive as a species and are free to explore and discover, there are few limits to hamper humanity. Faith and science are complimentary, so long as dogma is restrained in each. It would be a tragedy for us to fail to achieve our full potentials. I do pray that all of our children and grandchildren take full advantage of what both science and faith have to offer.
We now have 39 posts (that includes my #1, which means there are really only 38) and 904 views. For every post there are almost 24 lurks.