Population size and molecular clock?

Jose Mª Muiño jmaria at teleline.es
Sat Jan 2 15:22:12 EST 1999


Guy Hoelzer escribió en mensaje <76ecbl$243 at net.bio.net>...
>In article <76ds4o$3q2 at net.bio.net>, Jose Mª Muiño <jmaria at teleline.es>
wrote:
>
>Ludvig Mörtberg escribió en mensaje <7604h0$7d9 at net.bio.net>...
>>Does population size affect the speed with which the clock ticks?
>>Assume that the mutations are neutral and must be fixed or lost in a
>>population through genetic drift. Any clues? I read a genetics book
>>about this but couldn't figure it out.
>
>It is a fundamental principle of the neutral theory of molecular evolution
>that there is no relation between population size and clock rate.  The
>reasoning is as follows:  larger populations experience more neutral
>mutations, but each neutral mutation has a smaller probability of ultimate
>fixation.  These two effects of population size exactly cancel eachother
>out, so the rate of substitution for neutral mutations (i.e. the clock
>rate) is not affected by population size at all

    Yes, it is. But:

    Ayala proved that the variability affect the speed of evolution, no?
    If we have a high speed of evolution we´ll have a high variability, no?
    If we have a high variability we´ll have a high heterozygosity (H), no?
    if we have a high heterozygosity (H) we´ll have a high Ne, no?

    Which is the problem?



larger populations experience more neutral
mutations (2NeV), but each neutral mutation has a smaller probability of
ultimate
fixation (1/2Ne). Yes, but if Ne is very high some mutations can be the
same, and this 2NeV news mutations are less (i.e: 2NeV-x, where x are
mutations not news). Then K isn´t the same than V, isn´t it?










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