PZ Meyers struggles with High School Biology

[Crucible]

http://scienceblogs.com/pharyngula/2006 ... henism.php

PZ tangles himself with his failure to understand High School level biology

yet another demonstration of the fact of evolution, and an exploration of mechanisms of evolution—showing that evolution is more sophisticated than changes in the coding sequences of individual genes spreading through a population, but is also a consequence of the accumulation of masked variation, synergistic interactions between different alleles and the environment, and perhaps most importantly, changes in gene regulation.

Unfortunately, it's also an example of some extremely rarefied terminology that is very precisely used in genetic and developmental labs everywhere, but probably makes most people's eyes glaze over and wonder what the fuss is all about. I'll try to give a simple introduction to those peculiar words, and explain why the evolution of a polyphenic pigment pattern in a caterpillar is a fascinating and significant result.

Students are usually taught a grossly oversimplified version of genetics. Everyone who has gone through basic biology has heard of Mendel and his pea plants, and the simple traits that assort independently and can be traced back to a single locus by their pattern of inheritance. There is one wrinkled gene, for instance, and it makes peas wrinkled. Unless you are defining things solely on a molecular level, however, there is no such thing as a phenotypic property that is solely the product of a single gene. Traits are polygenic, meaning that multiple genes cooperate to produce a a phenotype. One pet peeve I (and many other biologists) have is the media shortcut of describing an identified gene as a "gene for X", whether X is breast cancer, schizophrenia, or hematopoiesis. Multiple genes contribute to all of those phenomena, and that's what we mean by polygenic.

PZ demonstrates that he is out of his depth, in attempting to penetrate the mysteries of high school level Bio.

He's tricked himself into word usage error over "phenotype" and ends up tricking himself into thinking that we are tricking ourselves into thinking that the allele makes a wrinkled pea.

That is what PZ thinks is being said.


However, it's only an allelic difference that makes the phenotypic difference "wrinkled" vs. "not wrinkled".

PZ has given a gross over-complication.

[JackBean]

sorry, but I don't understand what you're saying.

but I have already seen somewhere this gene for X wheter X is.... blah blah blah

[Crucible]

sorry, but I don't understand what you're saying.

but I have already seen somewhere this gene for X wheter X is.... blah blah blah

It's simply that the allele for "Wrinkled" does not have to be the thing that makes all the other things happen which goes into making a wrinkled pea.
It only has to be the difference that causes the phenotypic difference. The genetic difference does not cause a wrinkled pea to form or to exist - It only causes the observed difference to exist - It is very simple.

PZ grossly over-complicates it.

[Crucible]

Traits are polygenic, meaning that multiple genes cooperate to produce a a phenotype.

Wrong. Only polygenic traits are polygenic. Some trait differences have nothing to do with genetics.

This demonstrates that PZ always improperly substitutes the question "What makes that thing ?" for "What makes that difference ?".

[Crucible]

Sorry about the extra "e", as in "Meyers". PZ Myers.