Today's evolgen Double Entendre Friday deals with the genetic phenomenon known as incomplete penetrance. Ok, maybe this one isn't a double entendre, but more of a pseudo-homonym (can you guess what it sounds like?). When students in an introductory biology course are taught about dominance they learn about recessive and dominant alleles and maybe some special cases (codominance, incomplete dominance, etc). Incomplete penetrance refers to the unpredictability of certain dominance relationships. Take, for example, two alleles of a single gene ('A' and 'a') in which A is dominant to a. We expect all AA and Aa individuals to express the phenotype of the dominant A allele. In some cases the heterozygotes do not show any of the traits characteristic of individuals carrying the A allele. We would then say that the A allele is dominant to the a allele, but incompletely penetrant. Hehehe, it sounds like we're talking about sex.
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Hey, if we're descending to the Beavis-and-Butthead level, there's no better science than geology!
Subduction
Orogeny
Thrusting
Uplift
...and don't forget my favorite, penetrative cleavage.
Hmmm. These are all structure and tectonics terms. I guess we mineralogists are above this sort of thing?
And if you believe that, there really will be a pony under your tree come Christmas!