Role of yunk-DNA

A lot of evolution can be described as continuous, gradual change of
pre-existing structures. The change from a dinosaur front limb to a
bird wing can be described as gradual changes in arm proportions,
muscle strengths etc.

It is also true that the factors that control these properties can
also be expressed as variables: the timing of gene-expression (earlier-
later), the quantity of a certain gene-product (more-less),
concentration-gradients that control phenotypic traits (steeper-
shallower).

A trait (and gene-expression) can only vary in a continuous, gradual
way, if something in the genome varies in a continuous, gradual way.

For DNA, being digital code, this is not obvious. Digital code is
sensitive to change. A change in the coding region of a gene will
likely result in a non-functional gene-product. There is no clear
correlation between genetic change and phenotype change.

However, what can vary in a continuous, gradual way? DNA-length.

That's the role of yunk-DNA. It allows for the controlled and measured
introduction of variation in a population, making continuous, gradual
evolutionary change possible.

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