Re: 'Swerti' spelling
- Subject: Re: 'Swerti' spelling
- From: <g*@peoplepc.com>
- Date: Wed, 26 Oct 2011 23:07:31 -0400
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ï For those interested in these issues . . . . (
pallida / variegata )
See "Breeding Red Irises" self published by Dr. Dan
Meckenstock in his chapter "Related Genetic Systems". This is an excellent
treatment of anthocyanin and carotinoid floral pigment developmental pathways in
iris. Critical published citations are included. The significance of
pigment pathways in iris is particularly relevant to discussion of species
origin and history, such as the pallida / variegata topic mentioned in the
post below. Further, the independent genetic systems of plicata
and glaciata modifiy these pigment expressions. See page 88 for a clearly
presented argument for parallel derivation of pallida and variegata from a
common ancestral population. I happen to agree with Dr. Meckenstock on this
conclusion though he certainly does not need my opinion to support his well
documented conclusion.
Let me jump off here to personal conclusions
regarding plicata. Since the plicata genetic system is
an indicator of "jumping gene" activity, ( or a transposable
element in technical jargon = TE ), the following might be noted
regarding plicata inheritance. This is personal opinion and should not be
attributed to Dr. Meckenstock as I do not know him except through his book.
If this last proves to be in error, the error is mine. Plicata
modifies pigment _expression_ present in iris flowers. It is almost certainly
native to numerous iris species and clades as it is expressed in
the universal plant language of DNA. TE's frequently function with two
independent elements present on different chromosomes. ( yes, we know there
are type 1 and type 2 TE's, but lets stay on the general point ) This alone
means that normal crossing over cannot be assumed and simple Mendelian
inheritance should not be expected to fit observed progenies. The
_expression_ of TE's can turn independent genes on and off. They
can rearrange gene sequences on chromosomes by insertion / deletion /
duplication. This type of genetic variation by its very nature, is
not entirely predictable. TE's are well known to be latent for periods of
time only to reappear. In summary, plicata _expression_ alone is not likely
to be a reliable marker with which to unravel the historical genetic
tapestry of pallida/variegata. Naturally, the _expression_ of TE's in some iris
backgrounds may be more frequent than others. Additional ties of TE's
with retro-viruses and other non-genetic factors is strongly suspected and
more recently becoming documented. Maybe this is jumpin' to conclusions,
but I have questions about plicata as a useful ancestral
marker.
None of this blunts my enthusiasm for a good
plicata that grows well in the Northeast !
irisman646
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