Susan Erickson wrote:
Ok - I agree with the theory Rob is talking about. But I also
know that we are not the experts on what is or is not lost in
this type of breeding.
Not long ago it was reported that a pair that both displayed the
recessive (desired) characteristic were breed and the resulting
population had 1/4 or 1/3 that reverted to the 'absent' dominant
character. This character had been "breed out" of the parents
and should not have been available to surface. Mother Nature
still has the top hand in all of this.
I assume you are talking about the recent hubbub about plant genetics
that was released a few weeks ago. This gets more and more blown out of
proportion every time I hear it...
So, if I read the initial reports correctly (I'm working from a copy of
the paper), this experiment was done in Arabidopsis thaliana (a common
lab plant). The crosses were actually selfings of plants homozygous at
a given mutant recessive allele (Called 'HOTHEAD', no, i don't know
why). The mutant allele designated hth, the 'wild type' allele HTH.
So, these plants were hth/hth. The scientists noticed that a
non-trivial percentage of the offspring were hth/HTH (heterozygous).
This is, of course, not possible. *grin* However, the percentages
weren't 25-33% reversion. The authors report 10% (the number is getting
exaggerated over time).
Mendelian genetics dictates that we can only inherit the alleles that
our parents have. So, this is a really big deal. It should be
impossible for hth/hth to give rise to hth/HTH progeny. There are a
number of possible explanations given, the practical upshot of which is
there is a lot of work to be done. One of the best theories right now
is that there are long lived RNA molecules in the cell (remember,
DNA-RNA-protein) that serve as a template to 'correct' mutations at
this HOTHEAD locus. That would be interesting... But, before we throw
Gregor Mendel out the window with his peas, we need to confirm this
result for other gene loci. So far, it has only been observed at this
one. And only in arabidopsis (not in other plants, not in animals, not
anywhere else...). It can't be that common an occurance, or somebody
would have noticed it before.
Anyway, I think it is a far leap from this paper to suggest that there
is some sort of mystical force of mother nature that keeps genetic
diversity silenced in some fashion, ready for expression whenever the
plant needs it. Some small percentage of genes might have this 'backup'
capacity, but even with the best explainations we have for the hothead
phenomenon so far, this backup capacity would be corrupted or lost over
more than a few generations. I think for most purposes, mendelian
genetics will still hold. Just like for most purposes Newtonian physics
works (but we need quantum mechanics for really small stuff).
Genetics is still a complicated and mysterious thing, anybody who
claims to have it figured out hasn't been paying enough attention.
When we breed to intensify color or any other characteristic we
are in effect hybridizing to create a more beautiful species.
Yes, I would do it if I could. It is the nature of the beast
(man) to selective breed what he wants to see in his plants. As
long as we say species x species is still species we are going to
'beautify' the species. Heck, I would love a C. aurantiaca that
did not self before I could enjoy the color and line. I am all
for species that carry the desirable characteristics.
SuE
http://orchids.legolas.org/gallery/albums.php
That was exactly my point, said far more adeptly than I could. We are
hybridizing when we breed species.
--
Rob's Rules:
http://littlefrogfarm.com
1) There is always room for one more orchid
2) There is always room for two more orchids
2a) See rule 1
3) When one has insufficient credit to obtain more
orchids, obtain more credit