Dominant/Recessive Genes

gc genecutl at
Sat Feb 26 13:45:06 EST 1994

In article <1994Feb26.164754.16156 at>,
se040 at (Mark Joseph Johnston) wrote:

> I am a computer science student working on genetic algorithms and want to ask
> a "silly" question.
> Recessive genes are generally not "good" for the organism, yes?
> If so why do they exist? Why do two alleles exist together?
> Is it to conserve genetic diversity (without manifesting a trait 
> with a poor survival value??
> Forgive my ignorance.
> Cheers.
> Mark
> %^).

You're asking your question as if life was designed rather than evolved.
If a detrimental mutation occurs which is recessive, it will only be
selected against in homozygotes.  Heterozygotes for the recessive
mutation will experience no negative selection.  Because of this, the
allele can persist for a very long time in the gene pool despite its
detrimental effects on homozygotes.
In simpler words, they happen at random and it's hard as hell to get
rid of them.

The question about maintaining genetic diversity is meaningless.  A
species does not decide to maintian genetic diversity.  Genetic diversity
or not is effected by selection on specific phenotypes.  Given a closed
population with a low mutation rate, a loss of genetic diversity would
be inevitable.  


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