Genetic Switches ?   Edward Frank
  Jun 27, 2007 23:03 PDT 


I have been thinking. Recently I read an article about researchers
investigating RNA molecules that seemed to turn on or off certain genes
encoded in the cell's DNA. The research involved finding cures or
relief from certain hereditary diseases. I know of a cave fish in
Mexico, that when it is grown in complete darkness under low food
conditions, it grows as an albino without eyes. If placed in an
environment with light and/or more food, the next generation is
pigmented and has eyes. So these drastic characteristics for the cave
adaptations are turned on and off in a single generation.

I am wondering about trees like the Live Oak and Sycamore that develop
such magnificent wide spreads and short trunks when grown in the open,
but grow tall with smaller spreads when grown in a forest setting. Are
the forms of these trees dictated by competition, or lack of
competition, on an individual branch by branch basis, or do they have
some sort of a genetic switch that turned on and off by the presence of
competition that dictates a general form the tree will take as it grows?

It has been noted in previous emails that biological forms do not
necessarily optimize for the best efficiency, but tend to do just enough
to get by. (They also progress by lurches when a particular adaptation
or mutation works well.) It would be better for the trees if they had
two different shapes to "choose from" rather than reinvent their general
overall shape with each tree.

All trees seem to express a shorter height and broader spread when grown
in the open. A tree of a particular species grown in the open tends to
have the same shape as others of the same species grown under similar
conditions. Different tree species have different characteristic open
grown shapes. Do they have a general forest grown shape to match, or
are the forest shapes simply a product of die-off and competition from
the less common programmed open-grown shape? That really sound kind of
silly to me that the more common occurrence, forest grown, would simply
e a sub-set of the generalized open grown shape for a particular

Ed Frank