Bio Help Hardy-Weinberg Equation???

Question

1750- brown eyes

250- blue eyes

A study on eye color was performed at an elementary school. The allele for brown eyes is dominant over the allele for blue eyes. Using the data given, what is the number of students in the 2000 sample that was taken that are heterozygous assuming the group is in Hardy-Weinberg equilibrium?

a. 210

b. 320

c. 480

d. 640

Answer 1

Well, first of all, the premise behind this question is entirely false because there is more than one gene involved in eye color.  But, if we just assume there is one gene for the sake of the question . . .

250 blue eyed people would all be bb (homozygous recessive).  That means the frequency of the homozygous recessive condition is 250/2000 or 0.125.  This is q^2.  That means q is the square root of 0.125 or 0.354.  Then p is 1-q and equals 0.646.

If p=0.646 and q=0.354, then 2pq = 0.457, which is the frequency of the heterozygotes.  The number of heterozygotes it the frequency times the total number of individuals, or 0.457*2000, which equals 914.  So, the answer is e. None of the above.