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theories of dominance

Brain Foley brianf at dna.uvm.edu
Mon Mar 22 18:20:29 EST 1993

	It seems to me that many theories of dominance and other such
theories are now a bit outdated.  We now know a lot more about gene
regulation, chromosomal inactivation via methylation, and other
phenomena to know that there is more to the story than just two
alleles both producing an equal amount of protein.
	I work with a gene that shows codominance in one cell type and
dominance in others.  In fact, the codominance is just scored as
dominance unless you use radioctivity to detect the actual level of
production in the heterozygote.  Their are so many ways to make two
alleles of a given gene.  One could have a defect in the promoter, so
that the different alleles make different amounts of an identical
protein.  One could have a stop codon in the reading frame,
eliminating the protein production.  One could have an alteration in
the Km, the Kd or the Kcat of an enzyme.  THe list is endless.
	Thus, the theory that covers all cases is hard to come by.
There are many genes that increase an individual's fitnes only when
present in the heterozygous state.  There are many that provide
"conditional fitness" (they help an individual living in some
conditions but not the same individual if it lives in different
conditions).  There are many that are detrimental if two functional
copies are not present.  There are many that are detrimental if two
functional copies are present.
*  Brian Foley               *     If we knew what we were doing   *
*  Molecular Genetics Dept.  *     it wouldn't be called research  *
*  University of Vermont     *                                     *

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