Recombination is introduced. Students are given parental genotypes for two genes and the distance between the genes. Students model recombination and segregation and determine all possible offspring phenotypes and their respective probabilities.

Students are given the results of a test cross from which they determine the order of three genes and the map distance between each pair.

Students are given the set of unordered tetrads that result from a cross. Students classify the types of tetrads, reason quantitatively about the types to draw qualitative linkage conclusions and calculate the map distance between the genes.

Students are given time of entry graphs for three E. Coli Hfr strains. Students determine the time of entry for each of the markers transferred by the Hfrs and map the markers and origin of transfer of the three Hfrs.