A trait due to recessive X linked allele in a large, randomly mating population affects one male in 10. What is the frequency of affected females?
The answer is 1 in 100 (How did the book come up with this solution) I have a final soon and this is one of the practice Q's.
X linked Genetics Probability Question?
Males only have one X chromosome, so if the trait affects them then they have the recessive x chromosome and if not they have the dominant X chromosome. The fact that 1 in 10 males are affected indicates that 1 in 10 X chromosomes are recessive for this trait. Females have two X chromosomes, and for them to exhibit a recessive trait they would both have to be recessive. Since the probability of a single chromosome being recessive is 1/10, the probability of both being recessive is (1/10)^2 = 1/100. Therefore 1 in 100 females is affected.
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