Kostas Kampourakis cautions us against teaching Mendelian genetics

A few weeks ago I put up a post on Were you lied to in your genetics class?. At the time I thought it was just a fringe view being expressed by a graduate student who didn't understand genetics but now I realize that it's much more important than that.

Kostas Kampourakis is a respected scientist who is being promoted by the National Center for Science Education (NCSE) as an excellent communicator of evolution. Here's a short video (below) where he explains why teachers are making a mistake by saying that Mendel is the father of genetics and that simple Mendelian genetics can explain complex traits.

I'm struggling to understand his point. Here's what I think he means.

Kampourakis uses the example of eye color in Drosophila. He agrees that segregation of the allele responsible for eye color may follow the Mendelian rules¹ but it's wrong to assume that there's a single gene responsible for eye color in fruit flies. He thinks that the goal is to understand the complexities of development and standard Mendelian genetics gives a completely distorted view of that subject, assuming, of course, that teachers can't separate genetics from understanding development.

Part of the problem is that we use the word "trait" differently. Take Mendel's example of pea color as another example. [Identity of the Product of Mendel's Green Cotyledon Gene (Update)] What Mendel was studying was the segregation of alleles in a gene called sgr (stay-green). It codes for an enzyme involved in the degradation of chlorophyll during senescence. When the enzyme is defective, chlorophyll isn't degraded and one of the visible phenotypes is that peas stay green instead of turning yellow.

I believe that the fundamental trait is the lack of an enzyme for degrading chlorophyll and this is what I would teach my students. I would also show them that the phenotype can be easily explained once you understand the biochemistry. It shows you that the connection between the fundamental trait and the visible phenotype can be mysterious so you should be careful about jumping to conclusions.

I think that Kampourakis sees this differently. He thinks that the example of green vs yellow peas is used to teach students that the color of peas is completely determined by a single gene. He thinks that the "trait" is the develpment of seed color in peas.

Kampourakis believes that "people looking for explanations and whatever happens to them in terms of disease and their own features, they find hard to reconcile the simplistic model that they have been taught with the realities of life." I think what he means is that students are being taught that single genes will always determine complex characteristics. He attributes that to the teaching of Mendelian genetics.

If he is correct, then that kind of teaching has to stop but I don't think it's the fault of Mendelian genetics. Mendelian genetics—indeed the entire field of genetics sensu stricto—is about the segregation of alleles. It is not about development even though we have come to learn a lot about development through genetics and the phenotype of mutants. I think that genetics and development are separate topics.

Kampourakis disagrees. He says, "we need, I think, to teach genetics from a developmental perspective. We need to show that genes do not determine traits but they are implicated in development." I believe this perspective comes from a more fundamental bias that distinguishes his worldview from mine. I tend to see genetics as a subject that covers all of biology and that includes all species such as bacteria, viruses, and single-cell eukaryotes. He tends to see things from a human perspective, which is much more complex than dealing with simple organisms. I think we should concentrate on teaching students about simple well-understood model organisms and then move on to explaining how this applies to more complex organisms. Kampourakis seems to be implying that we should jump right into reaching high school students about the most challenging issues in biology.

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1. Actually, the common allele for white eye in Drosophila (see image) is X-linked so it doesn't follow the standard rules for Mendelian segregation!