Cytachrome C and neutral drift

As the different versions of Cytachrome C all do the same thing, transport electrons, the existence of different versions in different species is due to neutral drift, right?
Is yes then I have a follow up question.

Thread moved here from the Proposed New Topics forum.

OK just to speed things up a little, I will assume that we agree that the different versions of Cytachrome C we see in different species are due to neutral drift.Why then do we not see different versions of Cytachrome C within species? (if this is correct which I underdstand it is).
Shouldn't we see different versions within species as a result of neutral drift within species?

I wonder what the answer is?Page Not Found | University of ChicagoThis paper shows the sequences for a wide range of mammels.. Just looking at it suggests to me that the differences are not a result of drift but are specific fixed mutations. That is the differences are small. It looks like something is conserving the sequences.It might be that you original supposition is wrong but I sure don't know.This message has been edited by NosyNed, 03-22-2005 08:37 PM

First, just because all versions of cytochrome C do basically the same job, it does not follow that there are no functional differences between them. For example (based on zero knowledge of the details of this particular protein), two versions might function best at two different temperatures. So more than drift might be involved -- but most of the observed differences probably are due to drift.Second, cytochrome C is a highly conserved gene, which means that relatively few nonsynonymous changes in its sequence are neutral, so you should see polymorphic sites pretty infrequently.Third, what makes you think that none of these sites are polymorphic? Looking at the UCSC genome browser, I see a dozen or more nonsynonymous single nucleotide polymorphisms in humans for the coding sequence of CYCS.

quote:

---

First, just because all versions of cytochrome C do basically the same job, it does not follow that there are no functional differences between them. For example (based on zero knowledge of the details of this particular protein), two versions might function best at two different temperatures. So more than drift might be involved -- but most of the observed differences probably are due to drift.
  —sfs

---

So if they are functionally different and even some differences are not due to neutral drift, can Cytochrome C be used as evidence for common descent?

I don't understand what the issue is here? Could you explain what the perceived problem is?

quote:

---

I don't understand what the issue is here? Could you explain what the perceived problem is?

---

I was under the impression that the various versions of Cytochrome C were used as evidence of common descent. That they display a kind of nested heirarchy.If there is no evidence that Cytochrome C does in fact undergo neutral drift within species then this may question whether it ever really neutrally drifts at all, and hence whether it can be used as evidence for common descent.I may misunderstand some things here but if you have the time I will try to pay attention to any help you can give.

I don't know anything like enough genetics to be able to help.I could guess but we would be better to wait for others.Meanwhile have a look at the pdf referenced in msg 4. It lists the genetic differences in cytachrome C for two or three dozen species.There seems to be a pattern.

Yes, Cytochrome C is part of the evidence for common descent. It is a highly conserved protein, so it only picks up very few changes. The patterns of difference fit the nested pattern of differences inferred by other means, which is a reflection of diverging lineages from common ancestors.The full strength of the evidence is not from a single protein, but the mutually confirming evidence of many genes and proteins. I have not read the paper you cite in detail yet; but it looks interesting. It considers not only the gene coding for this protein, but a closely related pseudogene.The Cytochome C protein is of special interest in the evolution/creationism debate, because of a creationist argument that used to be raised. It turns out that snakes have a sequence which is unusually close to the primate sequence, which means that snakes may place incorrectly in a phylogeny, especially if there are not a lot of close relatives for snakes included in the analysis, and if raw distances are used rather than a proper cladistic analysis. This is sometimes taken by creationists as undermining the case for common descent.Cheers -- Sylas

To make something that has been implied already clearer the rate at which cytochrome-C changes is slow - it is less frequent than speciation.That is not to say that it does not vary within ANY species but it does mean that we might have to look hard to find an example - and there may not be one at the current time.This message has been edited by PaulK, 03-23-2005 03:17 AM

quote:

---

To make something that has been implied already clearer the rate at which cytochrome-C changes is slow - it is less frequent than speciation.

​

That is not to say that it does not vary within ANY species but it does mean that we might have to look hard to find an example - and there may not be one at the current time.

---

What about sharks? Haven't they been around for an awful long time?
They should have been around for long enough to display variation.It certainly does seem a very weird coincidence if these varaitions only are within species if we take animals like sharks into account doesn't it?This is is what you seem to say is true that there may not be any real varaitions within species compared to those between species.

I don't get your point. You do know that "sharks" is not a species, I presume. I would expect certain amount of diversity in Cytochrome C within sharks. The amount of variation depends, amongst other things, on the time back to their most recent common ancestor. We should expect patterns of diversity that tend to line up well with phylogeny obtained by other independent means. Comparison with rays would be good also (I think they are close relatives).Do you have any information available on how much diversity in Cytochrome C there is between different species of shark?Cheers -- Sylas

If you want to argue that a modern species of shark has been around for a long time then I'd like to know which species, the evidence that it has been around that long and how much we know about the cytochrome-C for that species. Otherwise I don't see the relevance.

Please ignore this post, I just wnated to re-check my facts before posting what is in the following post.TTFN,WKThis message has been edited by Wounded King, 03-23-2005 05:23 AM