Final answer:
Phenotypic frequencies for Blood Types O, A, B, and AB are calculated using allele frequencies for IA, IB, and i alleles, with A and B as codominant and O as recessive. Blood type A results from IAIA or IAi genotypes, B from IBIB or IBi, AB from IAIB, and O from ii. Phenotypic frequencies are determined by the probability of inheriting combinations of these alleles.
Step-by-step explanation:
To calculate the phenotypic frequencies for Blood Types O, A, B, and AB in the human population, we must consider the allele frequencies of the three possible alleles: IA, IB, and i. The A and B alleles (IA and IB) are codominant, meaning that they are both fully expressed when present together (as in Blood Type AB). A person's phenotype for blood type is determined by the combination of alleles they inherit from their parents.
Blood type A can have genotypes IAIA or IAi, Blood type B can have genotypes IBIB or IBi, and Blood type AB has the genotype IAIB. Blood type O, which is recessive, has the genotype ii. The actual phenotypic frequency in the population is determined by the product of the probability of inheriting each allele from parents.For example, if the allele frequency for IA is p, for IB is q, and for i is r, then the frequency of genotype IAIA is p^2, IAi is 2pr (since there are two ways IAi genotype can be formed), similarly IBIB is q^2, IBi is 2qr, IAIB is 2pq (for Blood type AB), and ii is r^2 (for Blood type O). By summing up the frequencies of genotypes that produce the same phenotype, we can calculate the overall phenotypic frequencies for each blood type.