Re: Question: How to recognize mutations


<Bloopenblopper@xxxxxxxx> wrote in message news:1177169315.840194.221510@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Apr 20, 3:21 pm, r norman <r_s_norman@xxxxxxxxxxxx> wrote:
On Fri, 20 Apr 2007 19:05:01 GMT, lumin...@xxxxxxxxxxxxxx (Luminoso)
wrote:



On 20 Apr 2007 06:48:53 -0700, Bloopenblop...@xxxxxxxx wrote:

Okay, suppose we find an organism with a noticeable phenotypic
variation from most of its pals in its population. Is there a way that
we can tell that this variation is the result of mutation and not
recombination of existing genetic material, transposons, or gene
transference?
So for example, there's the famous story about peppered moths adapting
to the industrial revolution. Was this really the result of mutations,
or could it have been recombination of existing alleles? And how do we
know?

In that particular case you could do a genome analysis or
even something cruder like breed the black & white moths
and do some math on their progeny.

Full or partial genome sequencing can reveal much, although
it's a bit slow and expensive right now. The dif between
black & white moths, or dark or light people for that
matter, CAN be a matter of alleles, outright mutations or
processes that affect gene expression such as methylation.
Regardless though, it's POSSIBLE to find out. Whether you
can AFFORD to find out is another issue ...

The more important issue is whether anybody would be interested in
finding out. If the question is important enough, someone will
eventually persuade the funding agencies to loosen some dollars. If
the issue is Parkinson's or Alzheimer's or diabetes or some other
such, then you can be sure people are hard at work looking. If the
issue is moths turning dark, then you can pretty sure that nobody
would even bother setting a grad student on it (unless either the
major professor or the grad student was particularly obnoxious).

Okay, thanks for your answers everyone. So would I be correct in
saying that any process that results in the creation of a new allele
is by definition a mutation?

I think so.

There is no ulterior motive to my question, i.e., I am not a troll who
is going to come blazing in here thinking he knows it all better than
99% of scientists. I manifestly don't. What got me thinking about it
is, as r norman pointed out, a new phenotypic characteristic could
develop because of a different combination of pre-existing alleles
that get shuffled around in sexual reproduction (right?). That's a
factor we need to account for whenever we point to modern-day examples
of adaptation.

A related question: I have a popular science book on genetics and
evolution. It contradicts itself, saying in one place that all genetic
variation is the result of mutations at some point, and in another
that's it's mostly due to recombination during meiosis, with rare
mutations. So which is it?

It depends on what phenomenon you are trying to explain. Mutation is
more important in creating new alleles. Or rather, those kinds of mutation
which don't involve recombination are more important than the kinds of
mutation involving recombination. Only a tiny fraction of the new alleles
that appear result from crossing-over.

On the other hand, if you want an explanation for why your set of genes
is different from that of any of your ancestors, and different from
everyone else on earth, then recombination is the better explanation.

That is, mutation creates new genes; recombination creates novel sets of
genes. As slogans go, this one doesn't distort reality too badly.

.

Relevant Pages

  • Re: An introduction
    ... combinations of existing genes than from the individual mutation within ... Mutation may keep feeding into the possible new ... When selection acts, it acts upon phenotypic traits, not directly on ... alleles will under selection together. ...
    (talk.origins)
  • Re: Haldanes Dilemma - clarifications - and Felsenstein [LONG]
    ... We have a population of diploid organisms, with alleles which can be ... there is back mutation at a rate equal to forward mutation. ... Recombination is once per parent, ...
    (sci.bio.evolution)
  • Re: An introduction
    ... combinations of existing genes than from the individual mutation within ... Mutation may keep feeding into the possible new ... When selection acts, it acts upon phenotypic traits, not directly on ... alleles will under selection together. ...
    (talk.origins)
  • Re: Is the complexity of evolutionary change explainable?
    ... subsequent life descended it in a "biological continuity," possibly ... doesn't put the natural mutation rate in perspective. ... genes, new nucleotides) just the ones present in the population and how ... Mutation via recombination events create information by ...
    (talk.origins)
  • Re: Question: How to recognize mutations
    ... variation from most of its pals in its population. ... If a tranposon disrupts a gene, or changes the regularatory control of a gene, then that's a mutation. ... Even intragenic recombination would be a mutation if it resulted in a new allele. ...
    (talk.origins)
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