In a population with two alleles, B and b, the allele frequency of B is 0.73, indicating that p = 0.73 and q = 0.27. According to the Hardy-Weinberg equilibrium equations, p + q = 1 and p^2 + 2pq + q^2 = 1, the heterozygote frequency can be calculated using 2pq. Substituting the values, the heterozygote frequency is determined by the equation 2(0.73)(0.27). The discussion emphasizes understanding the application of Hardy-Weinberg principles to calculate allele and genotype frequencies in a population.