The gene frequency for an X-linked recessive disease is 1 in 1,000 in the general population. What is the frequency of affected males in this population?: (A) 1 in 10, (B) 1 in 100, (C) 1 in 500, (D) 1 in 1,000
Answer is D. If the disease frequency in the population is 1 in 1,000, and the disorder is X linked, that means that out of 1,000 men, 1 would have the disease because each man contains one X chromosome. Because women contain two X chromosomes, the carrier frequency is 1 in 500 because 500 women would contain 1,000 X chromosomes, one of which would contain the mutated allele.