The main materials for this exercise are sets of pedigree charts. We also use a coin and a marker pen which students can provide. The pedigree charts already have the circles and squares connected by lines. The phenotype charts have the same number and orientation of squares and circles connected by lines but are otherwise blank. The exercise involves filling in the genotype chart by tossing a coin to determine which of the two alleles is inherited by an offspring.
Instructors can make their own pedigree charts.
Alternatively one can use one's own or other families' pedigrees. Then decide upon the type of trait, dominant, recessive, or sex-linked recessive. Then keeping in mind the type of trait, pick the genotype for select individuals. First note the genotype for select individuals on the genotype chart. In the example given in Figure 1a , the father is heterozygous and mother is homozygous recessive.