In a sample of 400 men,48 have X-linked color blindness and all the others have normal color vision.If men are hemizygous for the allele,what is the frequency for the X-linked color blindness allele?
A) 0.1
B) 0.12
C) 0.24
D) 0.48
E) 0.88

Question

Quizplus · Accepted Answer

Since men have only one X chromosome, they can only have one copy of the X-linked color blindness allele, making them hemizygous. Therefore, the frequency of the X-linked color blindness allele can be calculated by dividing the number of men with the allele by the total number of X chromosomes in the sample (2 X chromosomes for each male).

Number of X-linked color blind men = 48
Total number of X chromosomes in the sample = 400 x 2 = 800

Frequency of the X-linked color blindness allele = 48/800 = 0.06

However, since the question is asking for the frequency of the allele (not the frequency of the trait), we need to double this result to account for the fact that each carrier female in the population will have one copy of the allele.

Frequency of the X-linked color blindness allele = 0.06 x 2 = 0.12

Therefore, the best choice is B.

In a Sample of 400 Men,48 Have X-Linked Color Blindness