identical mutations

Doug Yanega dyanega at MONO.ICB.UFMG.BR
Wed May 7 18:25:20 CDT 1997


Dave Williams wrote:

>>But if population geneticists believe that beneficial mutations *often*
>>have multiple origins, has this been taken into consideration by molecular
>>systematists, and/or is it considered irrelevant? Or am I missing something
>>and just asleep at the switch today?
>
>Do recessive mutations need to be identical to be identically effective? If a
>debilitating or liability laden dominant gene can be deactivated by rendering
>the protein associated with its locus ineffective through mutation then ANY
>such incapacitating mutation would be helpful, would it not? It seems likely
>that there may be several to many possible amino acid sites at which a
>substitution would change the tertiary structure of the protein. Thus
>beneficial recessives might easily have multiple origins. Am I genetically
>naive or missing something? How do we know, in the sense of classical
>genetics, that all recessive alleles are identical?

Actually, I think something is missing here - if the mutant alleles are not
identical but have similar effects, then they could NOT form homozygotes
(by definition) if they came together in a single individual, which was
what the original pop'n geneticist *explicitly* said was involved (because
unless they *were* identical and *could* form homozygotes, each mutation
would likely vanish from the population very quickly, being neutral in
heterozygous form).

Besides which, no one knowledgeable in molecular systematics has responded
to the original query (hellooo, Mr. Lyons-Weiler?). ;-)

Peace,

Doug Yanega    Depto. de Biologia Geral, Instituto de Ciencias Biologicas,
Univ. Fed. de Minas Gerais, Cx.P. 486, 30.161-970 Belo Horizonte, MG   BRAZIL
phone: 031-448-1223, fax: 031-44-5481  (from U.S., prefix 011-55)
                  http://www.icb.ufmg.br/~dyanega/
  "There are some enterprises in which a careful disorderliness
        is the true method" - Herman Melville, Moby Dick, Chap. 82




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