Does Mendel fit in contemporary high school curriculum?

Ken and I met Tuomas Aivelo in person last August when we were in Finland teaching Logical Reasoning in Human Genetics, though we'd known each other on Twitter for a while.  He's a PhD student in Ecology and Evolutionary Biology at the University of Helsinki, with a keen interest in how genetics is taught in secondary schools.  He frequently speaks and writes on this topic (e.g., here), and has been active in efforts to revise genetics textbooks in Finland and elsewhere.  He has a blog of his own, with a very large following (which I know because occasionally he links to our blog and it seems that most of Finland follows the link), but unfortunately for those of us who don't speak Finnish, it's in Finnish.  Google Translate has a long way to go to make sense of Finnish.  We're pleased today to have Tuomas's thoughts in this guest post on teaching genetics.

Does Mendel fit in contemporary high school curriculum?

By Tuomas Aivelo

It’s not too often one gets real eureka moments, but I had one of those last August. I participated on Logical Reasoning in Human Genetics course taught by Ken Weiss, Anne Buchanan and others in University of Helsinki. I promised to write this up for Mermaid's Tale (as Anne has been continuously complaining it's difficult to read my own blog Kaiken takana on loinen via Google Translate).

One of my self-set objectives for the course was to figure out what kind of curriculum high school (or as it's called in Nordic context – upper secondary school) biology should have. Finland is about to update its national core curriculum and I have a soft spot for genetic education so I have been involved in curriculum design.

The problems with genetics education are well-known: students have poor understanding of what genes actually are, how genes function and students are not able to perceive how 'gene' means different things in different fields of biology. Lack of understanding of scientific models is very pervasive in biology. While our peers in chemistry and physics education have done better work in explaining what scientific models are (i.e., “Bohr model”, “Standard model”), we have been overwhelmed by many different models for ‘gene’.

I remember when I for the first time understood that gene can actually mean multiple things. It wasn’t that long ago, probably in the beginning of my PhD studies. I wish somebody would have earlier told me this explicitly. Suddenly I understood most of the debates which transcend the fields of biology and involve genes are related to different meanings of genes in different fields rather than anything based on reality.

Scientific models are most of all helpful in making the reality more easily approachable for scientific inquiry. They are very powerful heuristic tools. The problem lies in genetic textbooks having several different scientific models of ‘gene’ which are not explicitly outlined as scientific models. A standard high school biology textbook can contain several, contradictory, gene models while not explaining why they are contradictory.

This all should cause worry as genetics education is actually very important. The most often discussed result of misconceptions in genetics is genetic determinism. Here I refer to the idea that traits are fixed by genes as genetic determinism. Genetic determinism excludes meaningful impact of environment out from the genotype-to-phenotype relation and it has never been scientifically sound theory.  (Genetic determinism can also refer to broader idea that genes have an effect on phenotype. This is obviously widely accepted idea. I’ve suggested the use of term “hard genetic determinism” to differentiate from “scientific genetic determinism."

School curriculum, teachers and textbooks are not the only problem, but also science journalism is rife with ”gene for” news. “A gene for a trait” is very deterministic view of gene function. The school should at least equip students with the tools to assess these news. The real problem lies in genetic determinism being implied to lead racists views and lack of intestest in personal behaviour in disease risk. In Logical Reasoning in Human Genetics course, Joseph Terwilliger also gave a good reason why every geneticist should be worried of genetic determinism. He attributed the people's worry of genetic privacy (for example, related to the insurance companies and job applications) to the overselling of genetic determinism: people feel unsafe sharing their genome because they think a meaningful understanding of them as humans can be simply read from DNA. Furthermore, this worry could lead to too strict laws which prohibit the use of samples and lack of consent for genetic studies.

So, the question is: what should we teach the students? At the moment, genetics education is dominated by Mendelian genetics. The canonical learning sequence in genetics starts with Mendel and his peas and works out pea pedigrees and segregation analysis. One of the central exercises is to figure out from pedigrees which kind of genotypes and phenotypes individuals have and which probabilities there are for a given phenotype to be expressed. This approach has been strongly attacked in last years. For example Michael Dougherty and Rosie Redfield (here and here) have attacked the Mendelian approach in genetics education in high school and introductory university courses, respectively.

There has also been defensive effort on the importance of the Mendelian approach. Mike Smith and Niklas Gericke argued that Mendel's work belongs to the general scientific literacy as it is a central part of our culture. Furthermore, they suggested that the chronological approach to genetics increases student motivation and understanding of the nature of the science. They also suggested using Mendel as an example that has heuristic value as a simple model of inheritance.

I'm not impressed with these arguments. If we have a culture of learning genetic determinism in school, purging Mendel from contents would only make it easier to change this culture. Historical or chronological approaches to different fields of biology are rare: normally genetics and evolution (e.g., Mendel and Lamarck-Darwin) are the only ones widely used. Furthemore, it is highly contentious if the Mendelian ”laws of inheritance” are actually a simple model of inheritance which could be used for a more detailed view of genetics. Simple, yes, but they work in very limited context. In fact, in contemporary teaching, while “the historical” aspect is often included, the contemporary part of the genetics is rather limited. In oursurvey of gene models used in Finnish high school textbooks, we did not find any modern models: all the models used were formulated before 1960s. We have an obvious problem: history is taking space from the contemporary understanding of genetics.

This is the point, when eureka comes to help: it’s not about Mendel or history. It’s not about the contents. It’s about what we are teaching at a more fundamental level.

Until now, Mendel and his peas have been used to answer how traits are inherited. In fact, the current Finnish curriculum notes that the course contents should address “the laws of inheritance”. The right question, as I see, is how the inheritance of the traits is studied. Let’s not focus on how inheritance happens but rather how we can study this phenomenon. Here we are at the heart of one of the central problems in science education in general. In school, we learn how things are, rather than how we know.

When we present Mendel as an example of how early inheritance patterns were studied, it brings all the contentious concepts into the right context. 'Dominance' and 'recessiveness' are highly useful concepts in the Mendelian context. This approach would bring a natural possibility to discuss why Mendel used peas for his studies and how useful these studies are to infer the inheritance patterns of other traits. This would highlight what differences there are in inheritance of traits in humans and peas.

Obviously, this approach would lead to less dominant place of Mendelian inheritance in biology classes as then Mendel would be only one of the many approaches to study the inheritance of traits. In any case, it would still make it possible to have a historical approach or other innovative approaches to the teaching. It allows for an easy approach to the models in genetics and what they mean without making Mendelian inheritance the model, but rather one of many models.

The current trend in science education is to put the emphasis on the Nature of Science (e.g., what science is and how it is done) and socioscientific issues (e.g., how knowledge of science can be used by active citizens). The question of how things are studied obviously suits the Nature of Science emphasis nicely and it shouldn't be too much of a stretch to expect that the understanding of how inheritance is studied makes it easier to have informed decisions on inheritance.

One of the real problems in biology education is that the teaching strategies are rarely studied in classroom context. Only empirical testing can answer if this emphasis on why more than what and how leads to better learning in genetics.

Mendelian Inheritance: Basic Genetics or Basic Mistake? Part IV

So, if we are right that 'Mendelian' inheritance is fundamentally mistaken--or, at best, generally inaccurate and misleading--then what kinds of conclusions can we draw and how can some of the basic attributes of life be accounted for?  We have to assume that life evolved and that to a great extent means genes, broadly defined.  Indeed, we may be worse off than we think if, as we tried to show in an earlier post, even what a gene is, is elusive with current knowledge.

Waterhouse, A Mermaid

In our book after which this blog is eponymously named, we argued that there has been too much attention placed on evolution (and a competition-centered view of life at that), relative to the more ubiquitous properties found at life's other time scales--of development and maintenance of an organism, and of the interaction of factors on the ecological scale.

The idea of Mendelian inheritance, which is widely extended to the vast majority of gene-trait relationships that clearly are not following the monk's principles, is of discrete states one of which dominates in their various combinations.  This was (and is) extended to evolution, with our grossly inadequate 'winner take all', 'survival of the fittest' notion of one best -- fitness-wise dominant -- variant that natural selection favored into success just as surely as a dominant allele was favored ineluctably into manifestation in the organism.

But if you think of the other properties of life, which we center our book around and will briefly name here, you might ask how Mendelian thinking, which only by deep contortions can be related to those principles, could ever have taken hold, unless it's by what amounts to an ideology, a takeover of a certain highly deterministic, simplistic view of the living world--a view that simply, for decades, wrote off into alleged irrelevance the actual way in which organisms work.

Sequestration and modularity
From DNA on up, life is organized as hierarchically nested partially sequestered units.  DNA has functional sequence elements arranged  together along chromosomes, but partially isolated in that they can serve their individual functions.  The units (such as amino acid codons) are repeated many times.  Proteins have partly separated functional units, too.  Cells are packaged units that have many different partially isolated subunits within them, such as organelles like mitochodria, isolated areas like the nucleus, and local differences in what is present in the cell membrane (e.g., a cell may have a front and back end, so to speak).

An organism (or even collections of organisms as in bacterial biofilms) is made of large numbers of cells.  These are repeated units that communicate with each other via combinations of signaling and other molecules, and this is what leads them to express particular, context-dependent sets of genes.  So that they are repeated, but different.  This process occurs hierarchically during development, and in response to environmental changes during life.  An organism is divided into organs and organ systems, like brain, heart and vessels, digestive organs, and so on.

Organs are made of nested, repeated units.  Intestines are segmented along their length, and their surface is littered with repeated structures called 'villi'.  Skeletons are made of repeated, partially different but interaction bones.  Trees are made of leaves and so on.  Plants and animals alike are constructed by repetition and branching.

Yet, importantly, each organism has only the one genome that it inherited from its parents!  So the same genome makes brains and braincases, that are as different from each other as any two things in all of life.

These processes are both qualitative: each leaf or bone is a separate structure; and quantitative: each such structure is somewhat different.  This is the natural variation that is the material on which evolution can work.

If you just think about this, you would have to wonder how it could be brought about by Mendelian inheritance.  How could just two states at a single gene be responsible for such complexity and quantitative internal organization?

It is perhaps easier to see how breaking a gene could cause a major state change, and thus a normal and dead alternative at a gene could be manifest in Mendelian inheritance terms.  Or if the trait is very close to a protein coded by a single gene, two major alleles (variants) at that gene could have big differences (yellow vs green peas, for example).  But as a rule, Mendelian inheritance makes little sense.  Partly that's because, as mentioned in earlier parts of this series, we confuse inheritance of traits with inheritance of genes.  Genes--specific stretches of DNA--are clearly inherited in a Mendelian way (with some exceptions that don't matter in this context here).  But traits generally are not.

The reason for all of this is that the basic principles of life, that include the above descriptions (see our book for detailed discussion in this context), involve cooperation--that is, co-operation or contemporary interaction--among many different elements, each of them variable in a population.  What an individual inherits are sets of genomic variants from its parents.  The traits an individual manifests are the net results of these variants acting in the particular environments in which they find themselves.