The origin of new alleles

So did my original post actually bring up a valid point? Are alleles really a problem for YEC, or will they be able to weasle their way out of it like everything else? Young Earthers seem to be very good at explaining away anything that is brought up as evidence against their hypothesis.And just out of curiosity, what is the REAL genetic mechanism by which dogs diversified from wolves 15,000 years ago? One YEC article I read was that no mutations were involved: only recombination. If so, where did the genetic diversity come from?

New alleles that have no history are obviously a problem for anyone who believes that only the touch of supernatural can create. Not all YEC's are so dogmatic.The fun start when they have to confront evidence of evolution going one way and then the other - and where both have to be due to loss of information or genetic material by their reasoning. The hand-waving away of evidence is quite something to see eh? Try them on the age of the earth -- see Age Correlations and an Old Earth: Version 1 No 3 (formerly Part III) for some talking points. But don't expect them to answer ... the usual response is some version of the "gish gallop" ... Recombination IS a mutation. Calling it something else does not stop it from happening. Given that dogs and wolve can interbreed - but don't naturally - the real mechanism would be population isolation that then led to an accumulation of mutations that differ in each sub-population. The cause could be the domestication of (proto)dog by man (nreote however that (proto)dog could be another related canine that was more domesticatable than a wolf).The dog ones have since been heavily selected by humans for a variety of purposes, and there is some discussion whether chijuajuas and great danes would breed naturally and hence may represent ends of what is known as a ring species.Above all, keep it fun eh?Enjoy.

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One thing important to this discussion is the role of meiosis and how that may play into the survival of new alleles that are passed along to the progeny by way of sex. There is a mechanical obstacle for new alleles in the first prophase of meiosis in the form of "crossing over," in which alleles may "jump" from one chromosome to the other. This may act as a homologous filter against new alleles and prevent them from eventually entering the gametes. The reasoning behind this is based on a well-reasoned theory that sex evolved to enable genes to escape their parasites (i.e., mutant codes). In this way at least some of new alleles could be treated as hostile to the genome.”Hoot Mon

Unless the mutation was sufficiently severe as to damage the chromosomal structure severely enough to prevent meiosis continuing how would this act as any sort of filter? All you would be doing in most cases would be exchanging which copy of a chromosome a particular allele ended up on, how would this act as any sort of filter to prevent an allele ending up in a gamete? In the case of gene conversion you might get an allele being completely replaced but that is as likely to be by the new mutant form as it is the wild type. You might get more cases where a recessive embryonic lethal gene was paired up with the same allele which would lead to the offspring of that gamete dying early in development but it wouldn't interfere with the actual formation of the gametes.Could you provide a reference to somewhere where this theory is actually put forward, because as it is it doesn't sound quite right to me.TTFN,WK

Please correct me if I'm wrong, but I was looking a crossing-over as a way to force processes such as nucleotide replacement and enzyme search-and-correction. These filter-like operations would effectively screen out mutated alleles. That way the genes avoid their parasites.”Hoot

AS far as I understand it you are wrong, but you aren't really saying anything specific enough to tell you how wrong.Perhaps you are getting crossing-over confused with mismatch repair. Some of the same enzymes or related ones are involved in both processes but the two processes remain distinct.As far as an allele being parasitic goes, that would only apply to deleterious mutations since if the mutation was not deleterious then the relationship would be mutualistic or possibly commensal rather than parasitic.TTFN,WK

Hi WK,Is this a new way of describing things? I've never heard the terms of ecological interactions being used to describe what occurs at the gene level - but then again I'm not a geneticist, so I may be out of it. I can maybe see viral insertions/retrotransposons as somehow "parasitic", but I don't get how other types of mutations could be considered "mutualistic" etc. Is this just a different way of looking at mutation, using borrowed terms (terms which, btw, even ecologists are now trying to move away from since the interactions they supposedly describe are way more complicated than the terms suggest)?

No it isn't, and it isn't a good way of doing it either. I simply used this formulation as Hoot Mon had decided to approach mutation in general, rather than specific things such as retroviral insertions, as a 'parasitic' burden on the genome and I was suggesting this could only be an accurate characterisation if the allele in question was detrimental.If we can consider a novel allelic variant to be parasitic in the context of a deleterious mutation, which may be propagated but at the expensive of a fitness decrease to the host genome, then I am just extending the analogy to consider a beneficial mutation, which would increase the organisms fitness and mean both that the novel allele would propagate and the host genome would also gain, as mutualistic.TTFN,WK

I'm not a geneticist, only a reader in that field. My readings of sereval good thinkers (e.g., Hamilton, Dawkins, Margulis, Hartl) have tweeked my interest in the biological implications of allelic origination, sex, death, and "genetic parasitism" (i.e., transposons or plasmids as digital "parasites"). I have taken sex to imply that advantages accrue for the genes, but not necessarily for their organisms, if there are other means of reproduction besides simple cellular fission. Sex might possibly be that advantage, and meiosis might be where genetic escape strageties take place; fertilization, too. Crossing-over seemed to me like a good bet. But I could just as easily be tripping through the tulips here, because most of this area of genetics is highly theoretical.Nevertheless, I am persuaded by Hamilton's arguments that genes are strategic in their efforts to avoid hostile configurations and survive. If deleterious plasmids, for example, enter the genome, the genes may have better options to avoid them if they can segregate themeselves through conjugation other more-complex measures of sex. That's the direction I was limping toward in with my previous post.”Hoot Mon

That's all moderatley tenable speculation but you did make one very specific claim that crossing over in some way acted as a filter for alleles during meiosis? Do you think you were mistaken about this?As I pointed out previously crossing over and gene conversion can lead to recombinations of genes which will cause any offspring to die early in development, but this is not the same as preventing them from becoming gametes in the first place.TTFN,WK

I'm not sure which organisms you're talking about (or which planet, for that matter) where plasmids enter the genomes of sexually-reproducing eukaryotes.Edited by crashfrog, : No reason given.

I certainly could be. I was looking for some specific explanation that crossing over occurs as a means to enhance genetic survival. The mechanics of crossing over seem like a lot trouble just to scramble the genes around; something else might be involved. So from there I speculated, foolishly perhaps. Do you have a model or a theory to explain the evolutionary value of crossing over?”Hoot

Frog, are you familiar with transposons? They are sometimes referred to as "mariner genes," but they are actually plasmids. The tsetse-fly genes we carry around are good examples.”Hoot

No, they really aren't. A plasmid is something very specific and transposons are not the same thing at all.A plasmid is a substantial genetic fragment which exists independently of the genome. There can be exchange of genetic material between plasmids and the nuclear genome but it is not the same as transposon activity.A plasmid may contain transposons but they are not the same thing.If you are going to go so wildly off the mark you should provide some references for your claims.TTFN,WK

Transposable elements? Yeah, I'm familiar with them; in fact, I worked in the very department where Barbara McClintock discovered them back in the 20's; I used to walk right past her greenhouse a couple of times every month. Hell of a lady. No, they're not. (I've never heard of them being called "mariner genes." "Jumping genes" is the common term.) They're genetic sequences that move from chromosome to chromosome within a cell. A lot of them are the result of viruses (retrotransposons), and about 45% of our genome is comprised of them and their remnants.Plasmids are circular segments of prokaryotic DNA used in bacterial conjugation. How would they get into eukaryotic cells? How would they integrate themselves into the genome? Viruses do that because they've specifically adapted to reproduce that way (and only that way), but most bacteria are too large to penetrate a cell, and the cellular organelles of eukaryotes are radically different than the cellular biochemistry of the prokayote cell. Are you maybe just making things up? Why would we have tsetse fly genes? Insects aren't viruses; they don't inject their DNA into hosts. (The worst thing they do is inject the parasitic Trypanosoma protozoan into the host's bloodstream, causing the much-feared "sleeping sickness.")