Suppose the probability of an a allele is p. If people mate randomly, then what is the probability of the (aa) genotype? 

Genetics

The estimation of allele probabilities is essential for the closer quantitative identification of inheritance. It requires the probabilistic formulation of the applied model of inheritance. The hereditary disease phenylketonuria (PKU) is a useful example. PKU follows a recessive form of inheritance. Suppose there are two alleles at a gene locus denoted by a and A where the possible genotypes are (aa), (aA), and (AA). An individual will only be affected if the genotype aa appears (i.e., a recessive form of inheritance).