Genetics: We Don’t Comprehend the Vole Thing

_{Patrick

October 4, 2006

Biology, Science}

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Excuse the bad pun.

http://news.uns.purdue.edu/UNS/html4ever/2006/060914DeWoodyVole.html

As for genetic evidence…unfortunately it appears our knowledge is fairly limited.
A study on voles found that even though their chromosome numbers range from 17 to 64 between species and the X chromosomes in some species carry 20% of the genome and that females sometimes carry significant parts of the male Y chromosome…despite these variations in genotypes, all voles come out looking basically the same phenotype. Some species look so identical it takes a DNA analysis to tell the difference (other methods of determining species via physical examination cannot tell them apart). What it really comes down to is that we do not comprehend the mechanisms that control the expression of the genes. So this must be taken into account when interpreting the the evidence.

Comments

Yup after all this "evolution" a vole is still a vole. In "The Deniable Darwin" David Berlinski puts it this way:
SWIMMING IN the soundless sea, the shark has survived for millions of years, sleek as a knife blade and twice as dull. The shark is an organism wonderfully adapted to its environment. Pause. And then the bright brittle voice of logical folly intrudes: after all, it has survived for millions of years. This exchange should be deeply embarrassing to evolutionary biologists. And yet, time and again, biologists do explain the survival of an organism by reference to its fitness and the fitness of an organism by reference to its survival, the friction between concepts kindling nothing more illuminating than the observation that some creatures have been around for a very long time. "Those individuals that have the most offspring," writes Ernst Mayr, the distinguished zoologist, "are by definition . . . the fittest ones." And in Evolution and the Myth of Creationism, Tim Berra states that "[f]itness in the Darwinian sense means reproductive fitness-leaving at least enough offspring to spread or sustain the species in nature." This is not a parody of evolutionary thinking; it is evolutionary thinking.Que sera, sera.
Joseph_{October 9, 2006
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Wow, after reading this article, one wonders if DNA is used for anything at all in Voles... different chromosome counts PER SEX!sls_{October 9, 2006
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michaels7: "From the article, I assume this to be an anomaly, one most baffling. Or am I uninformed and are there other mamals which may be so constructed and surprising in genetic fluidity?" I recall attending a seminar a couple of years ago where a group complex of south american rodent species displayed a similar amount of genomic upheaval, but in that case I don't recall if the species were quite so phenotypically indistinguishable or not. Someone at work pointed out to me recently that the generation time for many voles is on the order of months (great_ape_{October 7, 2006
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great_ape, thanks for the lengthy response. I'll have to chew on your answer a bit, but the jist is we agree, there's much to learn. I'll continue to hold reservations however about macro-evolution and chimp/human differences. From the article, I assume this to be an anomaly, one most baffling. Or am I uninformed and are there other mamals which may be so constructed and surprising in genetic fluidity?Michaels7_{October 7, 2006
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After I first read the article, I thought, "We don't know anything about genetics." It's really a very perplexing paper. After chewing on it a little bit more, it strikes me that perhaps the 'vole' is an argument against the "central dogma" of molecular biology, meaning that the information contained in the cell's nuclear DNA is not as determinative as first thought. Maybe this animal argues in favor of the "cell", more specifically, the "ovum", as being the 'conductor of the orchestra', with the DNA simply being the assembled group of musicians.PaV_{October 7, 2006
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the blueprint/computer code analogy to the genome has its limitations Yes. At least one of the limitations is that we understand every last bit (pun intended) of the computer technology we have created and we can only compare it to the tiny pieces of biological technology that we have managed to reverse engineer so far.DaveScot_{October 5, 2006
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"I do not think this research favors either side, but makes a statement of how much more science still must discover." --michaels7 I could not agree more. I think what this does illustrate is how malleable and shifting the genomic landscape can be. However tempting and natural it is to adopt the digital code metaphor, the blueprint/computer code analogy to the genome has its limitations. There is something much more fluid and dynamic about dna in its physical embodiment and the way it does its job. And I think this vole phenomenon suggests --or even confirms--that genomes can accomplish much the same thing despite while being highly rearranged and reorganized. I need to read up on the geography of these various species, but the canonical explanation for this sort of phenomenon would likely be that reproductive barriers--either in sympatry (geographically overlapping) or at some point in allopatry (geographically separated) between the various species arose. No longer able to share DNA, their genomes were not able to be cohesive and homogenize, yet what it meant phenotypically to be a "good vole" remained constant for the various species. So the phenotype didn't change. Meanwhile, however, the shifting sands of their respective genomes continued to accumulate the sort of mutations, largely neutral, that resulted in this sort of genomic divergence between species. Through all that change, however, the core phenotype remarkably remained the same. It's very interesting and may indicate that the vole phenotype is a pretty steep and isolated fitness peak on the landscape, likely stabilized as well by a number of genetic networks such that, even if some of those genomic landscape alternations produced a change that had the biological *potential* to change the vole phenotype, it may have been buffered other aspects of the network which "locked in" the phenotype. Now contrast this phenomenon to the more or less minor changes and rearrangements between us and chimps--and the phenotypic change that result-- and it goes to show how much more we still have to learn.great_ape_{October 5, 2006
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Dave, I recognize this and appreciate his input just as I do most here. I try to learn from both sides, though I disagree with RM&NS for macro-evolution. Great_ape, you, Dr. Davi_son, all have information I try to soak up. I had posted the Voles article in comments(I thought) sometime ago and glad to see Patrick post it. I was hoping it might generate a good discussion between the two sides as to just how seriously little we do know of all the interactions and mechanisms which produce the living forms we see. I do not think this research favors either side, but makes a statement of how much more science still must discover. My questions are not always rhetorical or sarcastic. Sometimes that is hard to determine in this context. But it was a sincere request for his thoughts. My thoughts are/were there is a base set of instructions, a rules set, a genetic variational algorithym set, and a historical set. This does not include the access methods and error correction which is phenomenal to think about in communication and reactionary repair or kill mechanisms. The study done on the Voles seems to blow this speculation out of the water initially, at least morphologically. It seems that other regulatory factors weigh much heavier into the equation and that the access can be found or delivered thru any arrangement. But this is from an obvious pre-disposition of my software background. I realize great-ape is not dogmatic, so, hoping to get some thinking outside the box viz a viz JunkDNA, external environmental pressures, and findings just like this which Patrick posted.Michaels7_{October 5, 2006
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Great_ape is a wonderful example of the loyal opposition. That's why he's had free reign here for a long time. His knowledge is impressive, likewise his ability to correlate it, he's civil to a fault, and most exceedingly rare is an open mind free of dogmatic constraints.DaveScot_{October 5, 2006
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Patrick, "What it really comes down to is that we do not comprehend the mechanisms that control the expression of the genes. So this must be taken into account when interpreting the the evidence." Glad you posted this for discussion. I'd like to see Great_ape comments from an evolutionary perspective with this knowledge of Voles and new Junk DNA discoveries almost daily. If we do not fully understand today all of the mechanisms involved in gene expression and other regulatory interactions, I think it to bold to state RM&NS is the final mechanism for all diversity. I much prefer, "we do not know the answer" to one of overwhelming "facts" for macro-evolution. To try and tie this together, please see also the following article on Voles and JunkDNA: 2005, rodent social behavior and Prairie Voles, http://www.nih.gov/news/pr/jun2005/nimh-09.htm The paper states, "Far from being junk, the repetitive DNA sequences, which are highly prone to mutate rapidly, may ultimately exert their influence through complex interactions with other genes to produce individual differences and social diversity, according to Young." I'm curious if one were to do a meta-analysis of Junk-DNA in studies, how many would they find which act upon behaviors, morphology, disease, cancer, etc.? And what I'm really curious to know is comparison to social habits in humans. Promiscuity or Fidelity, Sobriety or Alcoholism.Michaels7_{October 5, 2006
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"Some of Triant's additional work explores the unique ability of vole's mitochondrial DNA to insert itself within DNA in the cell nucleus." Did they really mean unique? No other species studied so far do this?avocationist_{October 4, 2006
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"What it really comes down to is that we do not comprehend the mechanisms that control the expression of the genes." Whatever is going on, it is important to keep in mind that the cell is not run by the genes. The cell is quite active in regulation of gene expression.Mudman_{October 4, 2006
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