I don’t think a single-celled genome could be physically big enough to contain all the possible genes necessary to produce every subsequent living organism.
I don’t understand what that has to do with “was there sufficient genetic means and opportunity for a single-celled Last Universal Common Ancestor to produce diploid descendants without mutation.”
You’re right that an ancient genome wouldn’t be big enough to contain “all the possible genes,” but that’s a scenario so ludicrous that it isn’t worth discussing. So I’m not sure what you’re trying to say. I thought we were discussing whether the LUCA could generate diploid descendants without mutation. I’m sure it could, but it’s very hard to understand what the actual question here is.
BTW, some single-cell genomes are gigantic (check out amoeba genomes). Genome size has relatively little to do with an organism’s complexity or size.
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Yes, sorry; perhaps I should have reiterated more background. There seems to be some debate at the moment about the relative contributions made by gene shuffling (for want of a better word) and mutations towards the diversity of life. Ben wants evidence that there are thousands of mutations in every cell division, while George thinks the exact number is irrelevant, as it seems that William DJ thinks that mutations don’t play any part at all, as they are always “corrected” back to the original by DNA repair mechanisms. If William is correct, then every possible genetic potential must have been present in the LUCA, and available for the diversification of life by means which do not involve mutation. I think that was the point of George asking “But in the very beginning, one there was only one-celled life? Was there enough variation to make a whale?” I think the answer is no. I think George and Ben think the answer is no. Stephen thinks the scenario is ludicrous. But if William DJ stands by his: “Irreparable mutations require dysfunctional mutation repair, which is a severe selective disadvantage, leading to fast extinction of a population” then he must think the answer is yes.
I think you are mistaken about the “debate.” @benkirk is right that evolutionary change typically relies on standing (i.e. previously-existing) genetic variation, as opposed to just-in-time mutation. That, I think, is the substance of his discussion with George. If Ben has asked for “evidence that there are thousands of mutations in every cell division,” it is because he knows that’s not true. You are misunderstanding the discussion, I think.
He’s wrong, by a long shot. It’s not an open question; it’s basic genetics.
Of course it’s no. It would be more reasonable to ask whether homunculi ride around in sperm and eggs.
Yes. Francis Collins has pointed out that some of the vegetables on your dinner plate have a bigger genome than you do.
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Yes, indeed. But this was raised after he savaged me in his initial foray.
The answer to my question, I think you will agree, should have been “No” … not all this crazy-making denunciations, contempt and bullying.
The post that triggered his fury had nothing to do with any of this. I was making a little point about something said about mutations. Why would I have to lay a foundation about alleles to be able to speak about mutation?
@benkirk just went too far this time; he owes me an apology. But, really, the best thing might be if he never offers it. I’ve had enough of bleeding from eyes and ears ears and shock-wave concussion hemorrhages caused by his arm-waving frenzies.
Have a pleasant evening, @beaglelady .
George.
Oh for goodness sake… you asked the question poorly … and that’s why we are spinning around on this one now.
You used the phrase “genetic means and opportunity”… what on earth is That supposed to mean?
The question you should have asked is:
“But was there sufficient number of alleles for a single-celled Last Universal Common Ancestor to produce diploid descendants without mutation?”
The answer would be No. You were attempting a linguistic judo throw with the last piece “… without mutation”. But all it did was create confusion. If the first part of the sentence is structured correctly, the “without mutation” becomes the clincher, instead of the “confuser”.
George
Why not? Is there something about diploidy that you think must require mutation? I’m not sure you understand the terms here.
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When I asked Ben this question, I wasn’t trying to have him teach me anything. I knew the answer and he knew the answer. And he did everything in his power to avoid stating it.
When you ask “why not”, are you asking hypothetically?
Or do you really think that the first one celled animals had enough allele diversity in their nucleus to shuffle them around enough (say, God is doing the shuffling) and make a whale without a single mutation?
This would be the very first time I’ve heard this assertion defended. Is this your assertion?
George
That’s not the question I responded to. This is: was there sufficient number of alleles for a single-celled Last Universal Common Ancestor to produce diploid descendants without mutation?
Why did that become a whale?
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You are right. My apologies. I’m kind of bent a little on my little whale thing…
I’ll try to let the tension flow from my finger tips… onto the floor … instead of onto the keyboard…
@Hugh_Farey, my apologies to you as well… I have whales on my brain!
Here is my act of contrition …
I thought it was very interesting where the article talks about plants that have experienced a change in their state - - seemingly within the last 200 years or so !!!
I’d love to know how they determined that . . . .
Perhaps comparing an old sample with a current one?
George
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I think we’re all going round in circles! Essentially, we all agree that mutations do play a significant role in evolution, and are not “corrected away” as William DJ appears to think. Actually, if he reads these last few posts considering the absurdity of the LUCA having enough genetic potential to evolve into whales without any mutation at all, he probably agrees with us too. However, I believe he is correct that mutations occur in huge numbers all the time (I cited one source earlier, but it seems to be common knowledge) and that the vast majority of these are corrected. If William were to accept that some are not corrected, then he would also be correct that the vast majority of the uncorrected mutations prevent either the DNA or the organism to which it applies from enjoying increased reproductive success. Only a tiny minority contribute to evolution. That’s why it’s taken such a long time…
Nice post! Your 2nd to last sentence in the quote above is “Only a tiny minority [of mutations] contribute to evolution.”
Hmmmm… I think there is a better word you could use instead of the last: ‘evolution’. Evolution has a pretty long future to it, right? So any mutation discovered and entered into the “Log of Mutations” might appear to have no affect now - - but could turn into a bonanza later for a population to survive environmental pressures, or to exploit a different niche where pressures are not so extreme. For example, one of the reasons that proto-whales (with 4 legs) did so well is that the marine dinosaurs were all gone and there was now way more harvestable food (millions of fishies!) in the water than on the land… and the converse relationship regarding predators!
If that were my sentence, I would write:
Only a tiny minority of mutations contribute to population survival or individual reproductive success in the current environmental circumstances."
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Possibly. My guess is that even so, most mutations dribble away without leaving the slightest trace of their existence.
A scientific mind would not, nor could not, make such a sweeping generality without data to back it up. Even suggesting this, without the data, diverts the mind away from the constantly re-affirmed truth that what seems like genetic gibberish today may be the key to a life form’s survival (in the past or in the future).
George
It would be great if you would use the quote function on the forum so we can see what you are responding to.
The problem with your statement is that it is hopelessly vague. We know a lot about what happens to mutations, and there is no need to “guess” about many aspects of evolutionary/population genetics. What we still don’t know as much about is the extent to which mutations land in selectively neutral parts of large genomes (like ours). Estimates of the germline mutation rate have been available for several years, and this research is now turning up details of mutations patterns in humans (including some evidence for so-called “mutator” genes, which increase the mutation rate). You may be surprised at how many new mutations you inherited from your parents. Would you like to take a guess? This is not a ‘gotcha’ at all. It’s just an attempt to illustrate the point.
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You might want to read up on why humans can’t produce their own vitamin C. It is a result of a mutation (broken DNA) that has been around for a very, very long time.
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Perhaps someone could tell me how to find the quote function, then I’d be happy to use it. I’ve been experimenting, but without success so far. However, for what it’s worth, I am a scientist and I can, and do, make such a sweeping generality. Various sources suggest thousands of mutations per cell division, and I do not think they all contribute to the progress of life on earth. Nor do any of the subsequent remarks contradict this suggestion. Sure, some of today’s “genetic gibberish” may one day contribute to a life form’s improved reproductive capacity, and I am not at all surprised that I have inherited huge numbers of mutations from my parents. I also know why humans can’t produce their own Vitamin C. A few mutations are directly and immediately useful, and many others contribute to evolution in the long run. But most of them don’t. I must say I don’t really understand why people find this so controversial.
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Correct. For some reason, George is unwilling to to accept this and keeps returning to the straw man of pretending that I am claiming no roles whatsoever for new mutations.
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