big breakthrough in Evolutionary Biology

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Originally posted by Philip:
Not trying to interrupt; but could you or anyone briefly help me understand the Borg's grand perspective here? Is he YEC, OEC, god-of-the-gaps, or what?

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I've traced your discussions with earnest but have not seen you state your grand hypothesis of the cosmos, the biosphere, and/or the human-psyche (perhaps in 25 words or less; I wouldn't be offended by crudeness of words). Forgive my untowardness.

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Meagerly,

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Philip

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Philip, so far he seems to be intent upon attempting to overturn the ToE.He hasn't mentioned God, religion, Christianity, or positive evidence for any other theory which explains the evidence.At least, not that I have read.

Thanks,Perhaps, he prefers to leave out his motives and reasons, to show that he's non-biased. We might see, perhaps, later.

dear Percy,You say:
"I had somewhat the same reaction when I first read the article back in February, but you've missed the important point. The puzzle was how morphological changes that require multiple gene changes across chromosome pairs could come about given that they're so incredibly unlikely. The results of the study revealed that a single change to a dominant Hox gene on a single chromosome can have a dramatic impact on body plan by turning on or off multiple genes on other chromosomes."Q) Is the change so "incredibly unlikely" that it is non-random (directed) mutation?And:
"You probably believe the example illustrated in the article where six-legged insects evolve from multi-limbed crustacean-like ancestors is a case of loss of information or de-evolution, but it's actually an example of suppression of expression."Suppression of expression is de-evolution, since the genes are present but not expressed. Did the genes that are not expressed become redundant? I would like to see the entire sequence of the suppressed genes in distinct organism. That would make it easier to interpret the data. Otherwise, unwarranted conclusion jumping is all the authors do.
What I strongly object to is that the innocent reader is mislead by the presented figure. It does not cover their research at all.In addition, a leg is still a leg. Of much more interest would be the appearance of a functional wings in a "shrimp" by a single mutation.And:
"Insects evidently still have the information for multiple limbs, but information was added to their genome, specifically in Hox genes, instructing many of the limbs to not be expressed."This is also an unwarranted conclusion. It can only be concluded from (over)expression studies in insects and that is not what the authors did.And:
"The opposite process whereby an organism acquires limbs not previously present is, I think, well understood, but I have no reference I can provide."That's a pity. I think I know what you mean. It involves segment duplication."Perhaps someone else here knows more about this, but a couple possible avenues are obvious. Gene duplication is one where during reproduction two copies are accidentally made of a single gene."Q) Where did the first gene come from?And:
"Another is a Hox-like approach where one gene controls how many times another set of genes is expressed. It's a simple change from saying "five limb segments" to saying "six limb segments"."That's it, but it is not so simple as you think it is.best wishes
Peter

dear schrafinator,You write:"I never grew any bottom wisdom teeth. They simply do not exist.While you may consider it a "loss", I consider it a wonderful adaptation, because I didn't need to get any dental surgery."Adaptation to dental surgery?
The loss/gain of the wisdom teeth may be the result of a preexisting mechanism that influences gene expression and invokes variation in the human population. For instance, the Alu-sequences in humans may be responsible for differential expression of traits in subpopulations, but may even be responsible for father-son differences."When the land mammals which evolved into whales lost their limbs, it was an adaptation to moving through water."This has never been observed; it is extrapolated (and an unwarranted conclusion) from the fossil record. Besides, according to ToE whales did not loose their limbs but their legs changed into flippers.Horses used to have many toes, but now they only have one.Incorrect. They use only one "fingernail" to walk on. (By the way, read Spetner and what he has to say on horse evolution)The ToE doesn't require constant "additions", so you saying that it does belies your misunderstanding of the Theory.It may be so that --in your opinion-- evolution does not require constant "additions", but could you than please explain to me how a bacterium became a primate, or --simpler-- how a prokaryote evolved into a eukaryote?"All the ToE requires is change."Not entirely true. ToE needs upward change. I do not doubt the existance of variation (=change)."It might be change that leads to more complexity, or it might be change that leads to less complexity. IT doesn't matter."Please explain to me why --in your opinion-- it doesn't matter. Of course, it matters whether we find new genes in an organism or whether genes are inactivated. Your statement demonstrates that you do not know the ins and outs of evolution theory and the problems it is facing."It all depends upon what the environment selects for and what variability exists within the population."If there are no new genes/traits which provide adaptive advantage there is nothing to select.Best wishes,
Peter

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Originally posted by peter borger:
Adaptation to dental surgery?

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Please, Peter B., You are smarter than that. Were surgery not available, impacted wisdom teeth could be very disadvantageous.

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The loss/gain of the wisdom teeth may be the result of a preexisting mechanism that influences gene expression and invokes variation in the human population. For instance, the Alu-sequences in humans may be responsible for differential expression of traits in subpopulations, but may even be responsible for father-son differences.

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Right.... so?

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This has never been observed; it is extrapolated (and an unwarranted conclusion) from the fossil record. Besides, according to ToE whales did not loose their limbs but their legs changed into flippers.

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So.... extrapolation == unwarranted conclusion? You've just toppled all of human knowledge. I think I've mentioned this before.{quoteIt may be so that --in your opinion-- evolution does not require constant "additions", but could you than please explain to me how a bacterium became a primate, or --simpler-- how a prokaryote evolved into a eukaryote?

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"All the ToE requires is change."][/quote]Evolution doesn't require "additions" in the sense of the sudden appearance of whole new appendages or organs. Something isn't just born with a leg where its mommie didn't have one. You might get a little bulge of muscle that gets larger over many generations. This is really just change of existing structures, which you accept I believe, not whole new additions.{quoteNot entirely true. ToE needs upward change. I do not doubt the existance of variation (=change).][/quote]Upward change?

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Please explain to me why --in your opinion-- it doesn't matter. Of course, it matters whether we find new genes in an organism or whether genes are inactivated. Your statement demonstrates that you do not know the ins and outs of evolution theory and the problems it is facing.

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Please explain to me how it does matter as per the context of this discussion.

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If there are no new genes/traits which provide adaptive advantage there is nothing to select.

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True, and the species in question is in big trouble.------------------
http://www.hells-handmaiden.com

I have never been satisfied with Bonner use of word repression and re-represion of genes for I keep thinking of the word "shear" evertime I try to get further into an undertanding of the molecular biology of development. If the word to think about immediately prior in this line is regulatory, again I get stuck because of too many re:s etc.

"It may be so that --in your opinion-- evolution does not require constant "additions", but could you than please explain to me how a bacterium became a primate, or --simpler-- how a prokaryote evolved into a eukaryote?"interesting article about mitochondrion's closest prokaryotic relative:

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Nature 396, 133 - 140 (1998)

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The genome sequence of Rickettsia prowazekii and the origin of mitochondria

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SIV G. E. ANDERSSON*, ALIREZA ZOMORODIPOUR*, JAN O. ANDERSSON*, THOMAS SICHERITZ-PONTN*, U. CECILIA M. ALSMARK*, RAF M. PODOWSKI*, A. KRISTINA NSLUND*, ANN-SOFIE ERIKSSON*, HERBERT H. WINKLER & CHARLES G. KURLAND*

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We describe here the complete genome sequence (1,111,523 base pairs) of the obligate intracellular parasite Rickettsia prowazekii, the causative agent of epidemic typhus. This genome contains 834 protein-coding genes. The functional profiles of these genes show similarities to those of mitochondrial genes: no genes required for anaerobic glycolysis are found in either R. prowazekii or mitochondrial genomes, but a complete set of genes encoding components of the tricarboxylic acid cycle and the respiratory-chain complex is found in R. prowazekii. In effect, ATP production in Rickettsia is the same as that in mitochondria. Many genes involved in the biosynthesis and regulation of biosynthesis of amino acids and nucleosides in free-living bacteria are absent from R. prowazekii and mitochondria. Such genes seem to have been replaced by homologues in the nuclear (host) genome. The R. prowazekii genome contains the highest proportion of non-coding DNA (24%) detected so far in a microbial genome. Such non-coding sequences may be degraded remnants of 'neutralized' genes that await elimination from the genome. Phylogenetic analyses indicate that R. prowazekii is more closely related to mitochondria than is any other microbe studied so far.

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The Rickettsia are alpha-proteobacteria that multiply in eukaryotic cells only. R. prowazekii is the agent of epidemic, louse-borne typhus in humans. Three features of this endocellular parasite deserve our attention. First, R. prowazekii is estimated to have infected 20—30 million humans in the wake of the First World War and killed another few million following the Second World War (ref. 1). Because it is the descendent of free-living organisms2-4, its genome provides insight into adaptations to the obligate intracellular lifestyle, with probable practical value. Second, phylogenetic analyses based on sequences of ribosomal RNA and heat-shock proteins indicate that mitochondria may be derived from the alpha-proteobacteria5,6. Indeed, the closest extant relatives of the ancestor to mitochondria seem to be the Rickettsia 7-10. That modern Rickettsia favour an intracellular lifestyle identifies these bacteria as the sort of organism that might have initiated the endosymbiotic scenario leading to modern mitochondria11. Finally, the genome of R. prowazekii is a small one, containing only 1,111,523 base pairs (bp). Its phylogenetic placement and many other characteristics identify it as a descendant of bacteria with substantially larger genomes2-4. Thus Rickettsia, like mitochondria, are good examples of highly derived genomes, the products of several types of reductive evolution.

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so this is how eukaryotes began... they were infested by a parasite which produces ATP...Reminds me of water ferns (Azolla) that recruit algae (Anabaena) to do some protein & ATP synthesizing.