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Re: Genetic Reversals



In a message dated 95-12-20 11:26:30 EST, George writes:

>Usually, during vestigialization the genes for encoding the particular body
>part are suppressed by other genes, not eliminated from the genome. The
point
>of Dollo's Law is that when a body part is lost through vestigialization,
>natural selection has ceased to work on it, and it is very unlikely to
return
>spontaneously.

This is not really what I am talking about with chromosomal rearrangement.  I
am thinking of what are called "balanced translocations" in which the genetic
material is conserved but the chromosomal structures are altered.  This could
happen either with or without phenotypic changes.  

In human medicine we have what are called "ring chromosomes" which are
deformed chromosomes usually found with balanced translocations in
phenotypically normal people.  Such people cannot make normal gametes and are
usually discovered in the infertility clinic.  I envision a similar type of
balanced rearrangement (in which meiosis is possible) as part of the ordinary
process of chromosomal rearrangement in evolution.  It would most likely not
involve vestigilization or natural selection per se.  It would be like the
"neutral drift" as an irreversible step that just happens and causes further
isolation of an already genetically isolated group.

Art