Re: Mitochondrial Eve

Marcio Pie (
Thu, 20 May 1999 21:26:22 -0400 (EDT)

On Wed, 19 May 1999 wrote:

> I didn't say that a gene can change and still be exactly the same gene. In
> fact I said the exact opposite: "Of course if genes change then so can their
> mutation rates, but **if they change they are technically no longer the same
> genes they were before they changed**." I'll say that again: a gene that
> changes is no longer the same as it was before. So a gene that changes is
> NOT exactly the same gene. If a gene changes then it becomes a new gene, and
> so may have a new mutation rate. But if a gene does not change then it stays
> the same old gene and its mutation rate does not change.
I agree with Steve Clark. This argument is circular. I look
forward to see your reply to his comments.

> >
> > The definition that I've learned and that is in Futuyma's textbook says:
> >
> > "Allele: One of the several forms of the same gene, presumably differing
> > by mutation of the DNA sequence, and capable of segregating as a unit
> > Mendelian factor. ... ...DNA sequence variants, that may differ at
> > several or many sites, are usually called haplotypes."
> >
> Ah, now I understand the source of your confusion. In the above definition
> the phrase "one of several forms of the same gene" refers to the fact that
> they all produce the same basic product, though the products may differ
> slightly depending upon the mutation involved. It does not literally mean,
> however, that the alleles are all the same gene. The phrase "capable of
> segregating as a unit Mendelian factor" tells us that each allele can be
> treated as a separate inheritable unit, subject to Mendelian laws just like
> any other gene. If in fact alleles were literally all the same gene then
> they could not act as separable Mendelian units, because they would be
> indistinguishable. An allele is fundamentally a separate gene, so it can
> have its own mutation rate.

I'm sorry, but this is not what the text is saying. In fact, I am not an
ignorant in this matter and I've NEVER seen any paper or book in which
your definition is used. My limited mind can't understand how is it
possible for a gene to have a constant mutation rate if every time it
mutates (even a single IN-DEL in your definition) it is a different

> >
> > I've never read a paper where the authors referred to different haplotypes
> > of the same gene as different "genes." Since this is not my area of
> > expertise (I'm a behavioral ecologist), I recognize that I may be wrong.
> >
> This is because they usually are not thinking in terms of strict Mendelian
> inheritence, but in terms of the product being produced. This is one of
> those cases in science where the scientists themselves use the wrong phrasing
> and nomenclature for convenience, but are nonetheless well aware of what they
> really mean. It can, however, be confusing to someone who is not familiar
> with the subject.

Could you cite any paper in which your "definition" was applied? I don't
think so. I don't consider myself unfamiliar with the subject. Actually
someone doesn't have to be familiar with the field to notice that your
definition doesn't make sense.