An alternative to using the expanded binomial equation and Pascal’s triangle in determinin...

An alternative to using the expanded binomial equation and Pascal’s triangle in determining probabilities of phenotypes in a subsequent generation when the parents’ genotypes are known is to use the following equation:

where n is the total number of offspring, s is the number of offspring in one phenotypic category, t is the number of offspring in the other phenotypic category, a is the probability of occurrence of the first phenotype, and b is the probability of the second phenotype. Using this equation, determine the probability of a family of 5 offspring having exactly 2 children afflicted with sickle-cell anemia (an autosomal recessive disease) when both parents are heterozygous for the sickle-cell allele.