Question

In humans, the COL1A1 locus codes for a certain collagen protein found in bone. The normal allele at this locus is denoted with S. A recessive allele s is associated with reduced bone mineral density and increased risk of fractures in both Ss and ss women. A study of 1,778 women showed that 1,194 were SS, 526 were Ss, and 58 were ss (Uitterlinden et al. 1998). Are these two alleles in Hardy-Weinberg equilibrium in this population? How do you know? What information would you need to determine whether the alleles will be in Hardy-Weinberg equilibrium in the next generation?

Answer 1

To assess Hardy-Weinberg equilibrium for the COL1A1 locus alleles, one would apply the Hardy-Weinberg principle using observed genotype frequencies, and check if the population satisfies the necessary conditions for equilibrium. The five main conditions required for Hardy-Weinberg equilibrium are a large population size, random mating, no selection, no mutation, and no migration.

Step-by-step explanation:

To determine if the alleles at the COL1A1 locus are in Hardy-Weinberg equilibrium, we must apply the Hardy-Weinberg equation: p² + 2pq + q² = 1, where p represents the frequency of the dominant allele (S) and q the frequency of the recessive allele (s). Given the observed genotypes (SS, Ss, and ss), we first calculate allele frequencies: p = the frequency of S, and q = the frequency of s.

In the given population of 1,778 women, there are 1,194 SS individuals, 526 Ss, and 58 ss. By counting alleles, there are (2 * 1,194) + 526 = 2,914 S alleles, and 526 + (2 * 58) = 642 s alleles. The total number of alleles is 2 * 1,778 = 3,556, so p = 2,914 / 3,556 and q = 642 / 3,556. We can plug these into the equation to see if the observed genotype frequencies match the expected frequencies under Hardy-Weinberg equilibrium.

For these alleles to be in Hardy-Weinberg equilibrium in the next generation, we would need to ensure that the population is infinitely large, that there is random mating, no selection, no mutation, and no migration. If these conditions are met, the allele frequencies should remain constant.