Why So Blue?

Remind students that Punnett squares help us determine all possible genotypes for the offspring of hypothetical parents, not what offspring are actually produced. In general, the individual offspring of specific parents are not important to our understanding of genetics; instead, we must look at genotypes and phenotypes at a population level. One easy way to approach this is to use ratios and frequencies.

Hand out the Ratios and Frequencies Student handout. The dominant allele (P) has been bolded in several places on the handout to help visually distinguish it from the recessive allele (p). Using the Punnett squares as simple examples, walk students through the difference between genotypic and phenotypic ratios, and show them how to calculate allele frequency. They will be applying this to a later activity related to the Fugate family. Reinforce for students that this is the same process used with data from entire populations and is not restricted to simple Punnett square examples.

After the students finish the calculations, pass out The Blue People of Troublesome Creek handout. Have students use the Why-Lighting strategy to address the question: "Why did the Fugates have so many blue-skinned family members?" Students should read, and when they find something that they feel contributes to the answer, highlight that portion and write their reasoning for the highlight in the margins.

When the students are done with the article, have the class complete an I Think/We Think exercise. Students should compare what they highlighted with a partner, and then the pairs share their most important idea or ideas with the whole class.