Flat Vines

pumpkins@mallorn.com wrote:
> 
> Hi-Has anyone pollinated a good plant with a flat or double vine?

First a genetics lesson:
  While you may not be able to define the terms Expression and
Penetrance, you already understand them to some extent. You are aware
that some (most?) genetic traits in humans (especially) vary in
expression from barely visible to very troublesome. Variable expression
of genetic traits in humans is so common that in the early years of
serious efforts in human genetics, many geneticists wondered whether
Mendels laws of genetics fully applied to humans. 
  The two terms overlap somewhat in common misuse. 
  Penetrance refers to whether all individuals who carry the allele show
it. Since some people with the dominant gene for 6 fingers (and toes)
have only five fingers, that allele has incomplete penetrance.
  Perhaps, most people with 6 fingers have different sizes of the extra
finger or other other effects. That is variable expression. A nice
example is colored fur on the feet of rabbits and cats. The whole rabbit
carries the gene for colored fur, but only the feet are cool enough for
the enzyme to make color. Keep the rabbit in a warm room and he will be
all white or in a slightly cooler warm room only the very tips of his
legs have colored fur. 
  Perhaps, flat vines in pumpkins has incomplete pentrance. Perhaps it
it controlled by a gene(s) but not all plants carrying it express it.
Indeed, different vines on the same plant vary in expression of flat
vines. It is possible that all pumpkins carry the gene for flat vine,
but another gene(s) or conditions increase expression.
  Since the whole plant carries same genes, it is more likely some
condition causes the variable expression.  
 This year we have had Hot and Cold weather. Perhaps one of these or
both affects expression of flat vine. If we rooted cuttings from a flat
vine and then grew them in various temperatures or fertility conditions,
we might find flat vines under certain temperatures and/or conditions.
Such temperature sensitive alleles are the most common kind of mutant
allele.
  If there is a gene(s) for flat vines, its expression may vary
depending upon whether other genes are present. Therefore, we do not
know wether all seeds from a fruit will give rise to flat vines. 
  Side vines arise at the tip of the plant by a pinching off of the
apical meristem into the apical and a smaller side meristem. Perhaps
temperature affects some aspect this pinching so that later we see the
absence of side vine. Actually we seem to get the side vine, it seems to
be the apical part that is defective--too much pinching. 
  All books I have read say we do not understand the mechanics of
division of the apical meristem to produce side branches.
  We should be able to find answers by
1. collecting data and looking for a pattern
2. testing clones of a flat vines under various conditions. This would
be my choice. 
3. make a list of the conditions which seem to be involved: temperature,
vigorous growth, hormone balance, presence of other genes, etc.


-- 
Harold Eddleman Ph.D. Microbiologist.       i*@disknet.com 
Location: Palmyra IN USA; 36 kilometers west of Louisville, Kentucky
http://www.disknet.com/indiana_biolab



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