Once you have calculated the genotype frequencies that you expect if the H-W equation is true, you need to calculate how many individuals that corresponds to. To do this you multiply each genotype frequency times the size of the population. For our starting example this means:
Expected homozygous dominant (AA) individuals = p2 x 1274 (number of individuals in the population). This is 0.202 x 1274 = 257.4
Expected heterozygous (Aa) individuals = 2pq x 1274 = 0.495 x 1274 = 630.6
Expected homozygous recessive (aa) individuals = q2 x 1274 = 0.304 x 1274 = 387.3
NOTE: your expected values will typically not be whole numbers, which seems a little odd, because you cannot have fractions of an individual. However, for the purposes of the statistical test we're going to be using, fractional answers are reasonable. You can check to see if your numbers are reasonable by adding up your expected values. They may be off slightly due to round effects, but they should be close to the 1274 population size you are working with. If there is a large difference check your work - there may be an error in there somewhere!
Now that you have your expected genotype numbers, you can move on to perform the statistical test that will let you determine if the population meets the Hardy-Weinberg requirements or not.
Expected heterozygous (Aa) individuals = 2pq x 1274 = 0.495 x 1274 = 630.6
Expected homozygous recessive (aa) individuals = q2 x 1274 = 0.304 x 1274 = 387.3
NOTE: your expected values will typically not be whole numbers, which seems a little odd, because you cannot have fractions of an individual. However, for the purposes of the statistical test we're going to be using, fractional answers are reasonable. You can check to see if your numbers are reasonable by adding up your expected values. They may be off slightly due to round effects, but they should be close to the 1274 population size you are working with. If there is a large difference check your work - there may be an error in there somewhere!
Now that you have your expected genotype numbers, you can move on to perform the statistical test that will let you determine if the population meets the Hardy-Weinberg requirements or not.
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