Suppose we want to determine the expected frequency of alleles in a population. It is always easier to work from the known to the unknown. So, start with the observed phenotypes. Let us assume that hand preference (right or left handedness), is, in fact, a two allelic system. (This may not be the case, but let's assume it true for this case.) So, those with a left hand preference have two recessive alleles (hh).

a. If we observe/survey our campus population and we observe that 75% of our subjects are right handed. What percent have homozygous recessive genotypes in our population?

b. Determine the frequency of the left handed (recessive) allele. (Hint: take the answer from your answer to a, and plug it into the formula. Find the square root).

c. What is the frequency of dominant alleles (H)? (Hint: 1 = the whole population, so subtract the answer you have in b from 1). (3 points)

d. Now plug the numbers you have into the formula and solve for the middle element, to establish the frequency of "2pq" (aka the percent of heterozygotes or Hh in the population - remember, these are genotypes, made of two alleles).

e. This is a ‘steady - state' (or ‘equilibrium') in populations. This is a baseline, because, in fact, no populations remain in this state, because change occurs. What is this state called? What changes occur and how does this baseline help us to understand them?