1. Figure 23.2 shows both random and assortative mating; use this in discussing these terms. Remind students that population genetics studies tend to analyze one gene at a time, so mating can be considered to be random with regard to one gene, even though other genes may be affected nonrandomly.

2. Show photos of humans with various characteristics and discuss assortative mating.

3. Figure 23.3 illustrates the mathematics of random mating. A bowl of pennies can also be used to illustrate random mating, where students blindly select pennies as mates.

4. Another fun demonstration of random mating involves having students "mate" with their classmates, and working out the products using alleles of interest. The mating is made random by telling the students that the rule is no one can refuse you if you ask to mate with them.

1. To illustrate a gene pool, a bowl of pennies, a jar of colored marbles, or some other similar visual aid can be used; discuss the fact that each penny or marble can be seen as the contribution of one individual's genes.

2. List out the assumptions under which the Hardy—Weinberg equilibrium is attained.

3. Work out an example using allele frequencies of a simple genetic system that shows codominance (e.g. the MN blood types) and then work it again in a simple dominance system. Use plenty of examples so that the variables for allele and genotype frequencies become familiar.

1. It is critical that students understand that the only condition under which q can be derived by taking the square root of q2 is the condition of Hardy—Weinberg equilibrium, and that one must know whether the population is in equilibrium before one can mathematically derive q this way.

1. Figure 23.5 illustrates higher and lower fitness.

2. Work out examples using the coefficient of selection.

3. Show Figure 23.6 and discuss how subtle changes in phenotype can result in dramatic changes in fitness.

1. Figure 23.7 shows how mutation can produce novel structures that affect allele frequencies in a population.

1. The concept of genetic drift affecting small populations is easily illustrated with a coin flipping experiment using real coins.

2. There are commercially-available computer packages that also will run through exercises in genetic drift with various population sizes.

3. Figure 23.8 graphs results of drift over several generations in populations of different sizes; graphs such as these can be produced with the same commercial computer programs that run the drift experiments.

1. Show Figure 23.9 and discuss how persons heterozygous for the sickle-cell gene have increased resistance to malaria, an example of hybrid vigor.

1. Show Figure 23.10 and discuss gene complexes.

1. Figure 23.11 is a nice illustration of balanced polymorphism.

2. Figure 23.12 shows a case of balanced lethality and also gives a real-life example of a dominant mutant (Curly), which make for an interesting Hardy—Weinberg discussion.

1. Figure 23.13 maps the Drosophila polymorphisms discovered by Dobzhansky.