I was digging around for some good examples for a talk I am doing on mutation theory in a few weeks, and came upon this great paper in PNAS – Molecular Origins of Rapid and Continuous Morphological Evolution. Their argument? “tandem repeat expansions and contractions are a major source of phenotypic variation in evolution”. Hmmm…. it almost seems as if these repeats are functioning as parameters to a larger system. That reminds me of something…. Almost like parameterized evolution.
The paper has a great image of repeat-based morphological variation, too:
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The primary differences in the skulls are nose bends and midface length, which are governed by a repeat sequence in the Runxp-2 gene. By expanding or contracting parts of this repeat, it affects the shape of the face.
What is also interesting about repeats is that they are also much more mutable than other sequences.
So, it appears that evolution may be parameterized, with systems such as repeats governing what parameters can be modified in the course of evolution.