Example of genotype configurations for trio (father, mother, affected child) when null (left) and alternative hypotheses (right) are true. The left and right panels represent genotype configurations for a family consisting of a father (rectangle), a mother (open circle), and an affected daughter (filled circle). The pair of letters below each individual is the genotype at a marker locus. In these examples, the marker locus has 2 alleles, A and B, and each parent is heterozygous at the marker locus. In each panel, we present the genotype configuration that is most likely to be observed under the corresponding hypothesis when the A allele frequency is 0.5.