Can we do a Genetics reading assignment?

The New York Times is publishing a series of very good articles (11 so far) under the heading The DNA Age, about the social and personal implications of DNA sequencing. I'd like to find a way to require all of my BIOL 121 students read and think about at least one of these articles.

How could this work? I'd tell them they need to choose one of the articles to read, and that they will be asked to write a paragraph about what they've read, in response to an article-specific question I'll post. They'll be encouraged to discuss their chosen article with other students, face to face or on the WebCT discussion board, but will need to compose their own paragraph answers. To discourage copying I can have them submit their paragraphs to Turnitin as well as in answer to a WebCT quiz question. I don't know yet what kind of questions I'd ask them.

Marking this would require some extra grader hours - I'd give them a strict word limit for their answers but even marking 400+ 50-word paragraphs will be a big chore. More generally, I'd like to shift at least 5% and maybe 10% of the course mark from the midterm and final to in-class and homework activities. I guess it's time I read up on ways to incorporate peer evaluation into such activities and assignments. I'm getting hold of a book by Eric Mazur called "Peer Evaluation"; I hope this will help me shift much of the marking burden onto the students (who will learn an enormous amount by doing it).

I think peer-marking is one of the things that our new WebCT-Vista system is supposed to facilitate. I hope it's not too hard to use.

The first day of class

I've been thinking about changing what I do on the first day of classes. In past years I've basically done a fast information-dump about the course and then dived right into content (shaking them up with the role of natural selection in the origin of life).

But this year I'm hoping to shift all of the classes in this course to less information-delivery by me and more thinking and doing by them. And it's important do actually do this on the first day. So I'm going to be asking them for input on what they hope to get from the course.

I also think that my default expectations have been shifted by spending the past 6 months developing learning objectives for the first-year biology courses. Learning objectives need to be stated as actions the students should demonstrate ("can do X, can explain Y, can interpret Z", not just states we want them to achieve ("understands X, knows Y"). I'm going to tell the students this, in the context of introducing the existence of learning objectives, and then I'm going to ask them to write down for me, not what they want to learn or understand or know by the end of the class, but what they want to become able to do.

I expect this will take some prompting, so I'll give them some examples: "I want to be able to explain to my parents why my sister has Down syndrome"; "I want to breed healthier Siamese cats"; "I want to help save polar bears from global warming"; "I want to help develop an AIDS vaccine". These goals are rather lame and/or unreasonable, but their only purpose is to stimulate the students to think of other ones.

I'm hoping this activity will accomplish several things. It will give me feedback that I can use in later classes. It will give them a chance to influence the course. It will require them to write. They will be encouraged to discuss their responses with other students (I'm not sure yet how best to do this). Most importantly, they'll experience (not just be told) that they are expected to do things in class, not just sit passively and watch me.

How to teach about dominance

Yesterday the team of people teaching BIOL 121 had our second meeting to discuss our new learning objectives. One issue that hadn't been included in the list of objectives is dominance. I added it to the list on our Instructors' Blog, stated as follows:

Students should be able to define dominance as a particular relationship between the effects of two alleles; dominance is said to exist when the phenotype of the heterozygote is the same as that of a homozygote for one of the alleles (the 'dominant' one). They should also be able to explain that dominance usually results when a single copy of the normal allele is sufficient to give the normal phenotype when combined with a defective allele, and to predict phenotypes when given such information.

Students find this very difficult, I think mainly because they are encouraged in high school to blindly accept "Mendel's Rules", and think of dominance as resulting from some mysterious gene inactivation process. At the meeting I put forward the way I have been trying to teach this concept. I was (slightly) mortified to discover how many assumptions my explanation relied on (assumptions fortunately not shared by my colleagues), so I've been trying to build a better explanatory framework, using ideas they raised.

Here are the figures I would use. The first three figures would be introduced at the end of the first class about how genotypes determine phenotypes (yes, I know that's an oversimplification that ignores the massive effect of environment in real organisms...).

Figure 1: Introduce lactase and lactose intolerance:

.
.
.
.
.
.
.
.
.


Figure 2: Show a graph of how lactose digestion depends on the amount of lactase:

Students may need to be told that each tube contains the same amount of lactose.

(I don't know if students should be told that this is fake data.)
.
.
.
.
Figure 3: Show the questions I'll ask about this information at the start of the next class.
.
.
.
.
.
.
.
.
.

Here are the figures I would show at the start of the next class:

Figure 4: Show the first question again.

Students could be asked this question first, before being given the guidance suggested on the next figures.
.
.
.
.
.
.
.
Figure 5: Remind them of the graphed data.

I've made the original graph pale, and superimposed on it the labels and numbers appropriate to thinking about the amounts of lactase in adults.
.
.
.
.
.
.
Figure 6: Add bars showing how much lactose would be digested by each amount of lactase.

Students could be guided by asking them how high these bars should be.
.
.
.
.
.
.
.
Figure 7:

Now we're back to the original question. After the guidance all students should be able to see that adults with 5µg/ml lactase digest lactose almost as well as adults with 10µg/ml lactase.
.
.
.
.
.
Figure 8:

This question is intended to connect their understanding of genotypes to phenotypes. The answers should be: 0 = -/-, 5 = +/-, 10 = +/+.
.
.
.
.
.
.
.
Figure 9:

The +/- heterozygotes have almost as much ability to digest lactose as the +/+ homozygotes. So they will be lactose-tolerant, and we will describe the + allele as being dominant to the - allele.

This is a lot of figures. Ideally the students would have the time to try to figure most of the steps out themselves; the figures are my ideas of the steps their thinking should take.

This lesson should also build the idea that dominance and recessiveness are not properties of alleles in isolation, but properties of relationships between pairs of alleles.

I usually tell students to ignore confusing terms like 'partial dominance' and 'incomplete dominance' and 'co-dominance', and to instead just describe any other interactions between alleles and phenotypes using more informative descriptions such as 'blending' (e.g. many pigments) or 'both phenotypes are present' (e.g. blood types A and B).

The numbers on the graphs are made-up data. Real human lactase assays are usually normalized to the ratio of sucrase to lactase, which is too confusing to present here. But here's a nice graph showing how lactase levels decline and sucrase levels rise in rats (from a page by R. Bowen at Colorado State).