Re: 50% mutation
From: Gil Lawton (gillawton_at_earthlink.net)
Date: 02/21/05
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Date: Mon, 21 Feb 2005 00:48:39 -0500 (EST)
A,
I am not a biologist, but am in early stages of
self-teaching, with emphasis on evolutionary
theory, which I will examine first generally and
then as to data converging from the various
sub-disciplines of the field. However, my
ignorance thus disclosed, let me say that I have
read recently of at least one study in which the
results suggested the number of copies of a
gene can account for comparative degrees
of expression of a characteristic.
If this has been discussed on the NG by
others, please excuse, as I am a recent
newcomer.
In this stage of learning, I sense that a lot of
things being stated by some people are things
based partly upon hard data and partly upon
a priori presumptions. I do not offer this as
criticism, because intuition and creative
speculation sometimes guide testable
hypotheses that pan out. I would hope,
however, that those already well versed in
evolutionary biology would let us novices
know when the things they say are backed up
by hard data versus when they are speculating.
As a greenhorn, I began believing whatever I
read -- but soon found myself reading flat out
statements, spoken as from a cloud over Mt.
Olympus, but contradicting other voiced from
that same cloud.
g
"A.C.H." <br.hessels@planet.nl> wrote in message
news:cvb06a$rhm$1@darwin.ediacara.org...
>A lot of evolution is the result of quantitive changes. In human
> evolution, for example, more brain, less hair, less snout etc. etc.
>
> These changes are the result of changes in the regulation of genes;
> how much, when and where a certain gene-product is produced. (And not
> of changes in the gene-products themselves.)
>
> The thing i want to point out is that the variables more-less,
> earlier-later are one-dimensional. A mutation in a regulatory sequence
> results in a phenotypic change along one dimension.
>
> Now consider a situation of directional selection, a situation where
> some adaptive change is required.
>
> The chance of a favorable mutation, a mutation with with positive
> fitness, is exactly 50%. (since either more or less, earlier or later
> necessarily results in positive fitness.)
>
> Am i missing something?
>
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