Application of the Hardy-Weinberg model to a mixed population of Bar and wild-type Drosophila

Abstract:: Unlike most population genetics labs, which involve simulations with beans or beads, this lab provides an opportunity to study a population of living organisms. Using Bar and wild-type Drosophila, students compare allele and genotype frequencies to Hardy-Weinberg expectations. Because the Bar mutation in Drosophila is sex-linked and incompletely dominant, students can determine the exact genotype of a fly from its phenotype. These data are evaluated to determine which (if any) of the five Hardy-Weinberg assumptions have been violated. This real-data approach allows students to appreciate the value of this null model and helps the instructor to discover and correct students' misunderstandings of the model.

Read the Fine Print

An Introduction to Population Genetics

Abstract:: The evolution of populations is examined by simulations over 5 to 10 generations. Students use playing cards to simulate random mating, and then modify the mating to illustrate more natural conditions. With the addition of computer simulations, the same evolutionary principles may be applied to many generations. Discussion topics include the importance of genetic drift and mutation as the sources of raw material for evolution, the maintenance of recessive alleles in populations, and the role natural selection may play in changing allele frequencies.

Read the Fine Print

Abstract:: This laboratory exercise features a physical and computer simulation of Hardy-Weinberg equilibrium.

Read the Fine Print

Abstract:: Using Polymerase Chain Reaction (PCR), genetic variation in a laboratory population of Drosophila is characterized. The population contains flies with two variants of a molecular marker. DNA from individual flies is amplified by PCR, generating products which are either "long" or "short" when visualized on an agarose gel. Three PCR "genotypes" (long/long, long/short, and short/short) are distinguishable and should be present in Hardy-Weinberg frequencies. The exercise requires one session for grinding flies and preparing PCR reactions, and one for conducting and interpreting gel electrophoresis. PCR can be conducted with a standard thermal cycler, or using "hand cycling" with two water baths.