Essential Genetics 6th Edition by Daniel Hartl

Exercise 11

Two homozygous genotypes of Drosophila differ in the number of abdominal bristles. In genotype AA , the mean bristle number is 20 with a standard deviation of 2. In genotype aa , the mean bristle number is 23 with a standard deviation of 3. Both distributions conform to the normal distribution, in which the proportions of the population with a phenotype within an interval defined by the mean ± 1, ± 1.5, ±2, and ± 3 standard deviations are 68, 87, 95, and 99.7 percent, respectively.
(a) In genotype AA , what is the proportion of flies with a bristle number between 20 and 23?
(b) In genotype aa , what is the proportion of flies with a bristle number between 20 and 23?
(c) What proportion of AA flies have a bristle number greater than the mean of aa flies?
(d) What proportion of aa flies have a bristle number greater than the mean of AA flies?