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Pleiotropy: Cellular-Molecular
Evolution in Action.
My name is John Torday.
This lecture is one
in the series of lectures
on evolutionary physiology.
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Pleiotropy occurs
when one gene is used
for several seemingly
unrelated purposes,
not unlike manipulating
a Rubik's cube
with a gear pictured
on one of its faces,
showing up on other faces
of the cube as shown here.
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Yet we know that all the genes
of the organism
are present in the zygote
and are distributed throughout
during embryogenesis.
So there are underlined
principles
that may account
for the pleiotropisms.
Shown here are the origins
for the first principles
of evolution,
which could
hypothetically dictate
where in house
such pleiotropy genes
would be located.
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Such evolved pleiotropic traits
had their mechanistic origins
in such first principles
and then progressed
to form the various complex
traits of physiology
with reference to those
principles as evolution.
1:05
At the molecular level,
the functional evolution
of such traits
can be traced in a way
that cholesterol
has been exploited
by eukaryotes.
Starting with its synthesis
in response
to the rising levels of oxygen
in the atmosphere shown in A,
generating cholesterol
by a biogenetic pathway
require 11 molecules of oxygen
for 1 molecule of cholesterol
shown in B.
The integration of cholesterol
into the cell membranes
of eukaryotes
facilitated evolution
due to the thinning
of the cell membrane.
Increasing oxygenation,
metabolism, and locomotion,
the three principles
of vertebrate evolution.
Subsequently, cholesterol
evolved to form lipid rafts
in the cell membrane
as the infrastructure
of cell surface receptors
which ultimately evolved
the endocrine system.
Cholesterol being the substrate
for the steroid hormones
and vitamin D.
