Cambrian Explosion

Posted by Jochen Fromm-3 on
URL: http://friam.383.s1.nabble.com/Cambrian-Explosion-tp521557p521566.html


I have heard of Hox genes before, but not in the context
of the Cambrian Explosion. Looks like it is associated with
the evolution of Hox genes. Wikipedia says Hox and
"homeobox" genes are closely related to the body plan. They
are labels and markers, i.e. they assign the right identity
to particular body regions along the body axis (individual
hox genes are activated at different positions), but they
also control the development. This means they represent and
control the structure of the body at the same time, just
like the emotions (as we know from Psychology) signal the
state of the body and control the body at same time.
http://en.wikipedia.org/wiki/Homeobox

Does this mean that the code for embryonic development is
related to "meta" genes (transcription factors which
typically switch on cascades of other genes) ? Interesting.
The hox genes are therefore perhaps a code in a code ?
Changes in Hox gene number results in different phyla
and body plans, changes in Hox gene expression in slightly
modulated body plans with different numbers of segments, and
subtle changes in the details of a Hox transcription
pattern results in modified segments, see the following
article about "Shaping animal body plans in development
and evolution by modulation of Hox expression patterns"
http://www3.interscience.wiley.com/cgi-bin/abstract/34221
http://wwworm.biology.uh.edu/evodevo/lecture18/gellon98.pdf

-J.