Pleiotropy and constraints

Here's a nice video about pleiotropic cameltoes constraints in evolution.



Note that the definition of epistasis and pleiotropy should look like this:

Epistasis: Two or more genes affecting the same trait.
Pleiotropy: One gene affecting more than one trait.

Another great example of a pleiotropic constraint is the hedgehog gene in blind cavefish governing both jaw and eye development, which I mention at the end of this post about the evolution of complexity.