Re joke

Ben:

>Thanks Joe for the biggest laugh of the week:
<The yellow leaf gene is a dominant gene and dominant genes are 
<usually considered to be genes that produce a functional enzyme.

Are you now saying that the yellow leaf gene is NOT dominant!  I was 
under the impression that you have been claiming that the yellow leaf 
gene is dominant - that is, Yy is a yellow leafed hosta and yy is 
green.  That sounds like a dominant gene to me!  Dominant genes work 
because they produce a functional enzyme.  Do you have evidence to 
suggest that it is the "y" allele that is the functional gene and "Y" 
is non-functional?

Now, Ben, are you saying that the yellow leaf gene "Y" and "y" are in 
the chlorophyll synthesis pathway?  If so, then the "Y" allele would 
have to be a mutated allele that takes the precursor and produces a 
flawed pre-chlorophyll molecule that the next enzyme in the pathway 
can not use as its precursor to produce the next pre-chlorophyll 
molecule.  In that case the "y" allele shouldn't be called recessive 
and instead should be given a symbol such as Y+ or Y.g where the .g 
reads as subscript g.  Now, this could explain why the YY genotype is 
lethal because the pre-chlorophyll molecule it produces is a 
non-functional chlorophyll.  The Yy genotype survives because it 
produces a buildup of the yellow, non-functional pre-chlorophyll but 
the "y" allele produces normal chlorophyll, so the hosta has enough 
chlorophyll to photosynthesize.  Now Ben, if this is what you are 
saying, it would be VERY easy for you to prove this with the access 
you have to research equipement.  Why don't you take some yellow 
hostas this summer and analyze their chlopophyll and pre-chlorophyll 
molecules.  I would think some simple spectrometric experiments should 
provide the anwser.  

Joe Halinar



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