Question

Alkaptonuria, which is caused by a recessive mutation, occurs at the rate of about 1 in 360,000 people in North America.  What is the allele frequency for the allele causing the disease and what is the frequency of heterozygous carriers of the allele in the population of North America?  Choose the best answer.

            Frequency of the                      Frequency of

            the Alkaptonuria                      heterozygote

            allele                                        carriers

A)        1/250                                       1/500

B)        1/500                                       1/500

C)        1/125                                       1/250

D)        1/250                                       1/125

E)        1/600                                       1/300

Select one:

a. A

b. B

c. C

d. D

e. E

Answer 1

The problem gives you one genotipic frequency, with that you can calculate the allele frequencies and the rest of genotipic frequencies, using the Hardy Weinberg equation: p2 + 2pq + q2 = 1

So now, q2 is the frequency of the recessive homologous genotype (the ill people):

q2 = 0.000002

Then the recessive allele frequency is:

q = = 0.0016

Considering p + q = 1, then:

p = 1 - q = 1 - 0.0016 = 0.9984

The heterozygous frequency is 2pq, so:

2pq = 2(0.0016)(0.9984) = 0.0031

So the answer is option E) 1/600 and 1/300