Re: Discussion on Origin of Sports

0Jim:

>We are reviewing the technical aspects of three articles on the orign 
>of sports authored by Ben Zonneveld.

I wish I could give you the definitive answer, but it seems every time 
I think I am beginning to understand it all something comes along and 
gets me all confused again.  I saved about 25 genomic related articles 
last night and spend some time reading them.  I think the whole 
biology world is in for a major shaking up.  There are a lot of 
theories about evolution and how genes work that are going to need to 
be reexamined.  Some of this stuff may even have some implications for 
what you are interested in.

I'll go into some more detail once I get time to read Vaugh's article 
that I downloaded from the Internet site, but in the mean time I think 
we can dismiss Ben's idea of mitotic recombination as a significent or 
even any source for variegation/sports in hostas.

First, mitotic recombination is an exceedingly rare event, maybe 
occuring on the order of magnitude of 1 in 100 million.  They have 
been shown to occure in bacteria and yeast, but very special 
circumstances had to be set up to demonstrate that mitotic 
recombination occured.  It has also been shown to occure in fruit 
flies, again at a very low rate and again it was a very sophisticated 
experiment that had to be set up to show this.  

Mitotic recombination might have some significance in single cell 
organisms, but hostas are muticelled organmism with maybe millions of 
cells.  Even if you did have a mitotic recombination that took place 
it has to occure in a cell where the results of the recombination can 
be seen.  This would mean that the recombination would have to take 
place in an apical meristem cell where it or one of its descent cells 
were to form a bud that would then give rise to a shoot where the 
variegation is present.  A mitotic recombination for leaf variegation 
in a root apex cell isn't going to do any good.  

Next, there are 30 pairs of chromosomes in hostas.  The mitotic 
recombination has to occure on the one chromosome where the 
variegation genes are located, and not only on that chromosome pair, 
but also at the correct location on that chromosome.  

You are taking an event that occures maybe once in 100 million cell 
divisions, multiplying that by the probability that it will occure in 
just the right cell, which is probably 1 in 10 million, then 
multiplying that by 1/30 for the probability of it occuring on the 
correct chromosome and then multiplying that by maybe 1 in a million 
for the probability that it will occure at just the right location on 
the chromosme.  I haven't done the math, but the answer is a VERY 
small number.

This isn't to say that mitotic recombination does not occure in higher 
plants.  However, to the best of my knowledge no one has ever 
demonstrated mitotic recombination in higher plants.  Now, there is 
always the possibility that hostas contain a mutant gene that allows 
for a higher mitotic recombination rate, but I don't see any evidence 
for this.  

If Ben has done conclusive experiments to prove that mitotic 
recombinations occure in hostas and has had the results published in a 
peer review scientific journal, then I wish he would let us know about 
it.

Rearranging of l1 and L2 tissue is, as Sherlock Holmes would say, 
"Elementary, my dear Watson."  However useful rearranging l1 and L2 
layers may be for horitculture, they only rearrange existing 
variegation.  This isn't a cause of variegation.  Now, there are a lot 
of interesting debates that can occure from this topic.  For example, 
I have an all blue/green leaved sport of Great Expectations.  Now, can 
I sell this as THE orginal sieboldiana Elegans?

I need to review the Vaugh article before moving on.  

Joe Halinar

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