Final answer:
In a population where one male in ten is affected by a recessive X-linked trait, the frequency of affected females is approximately 1 in 100 (option B), calculated using the square of the allele's frequency in males.
Step-by-step explanation:
The frequency of affected females due to a recessive X-linked allele in a large, randomly mating population can be calculated by using the fact that these traits are more common in males than in females, as males have only one X chromosome and females have two.
If the allele affects one male in ten, the frequency of the recessive allele (q) in the population can be calculated as the square root of the frequency in males (since males are hemizygous for X-linked traits), giving us q = sqrt(1/10) or about 0.316. To find the frequency of affected females, we must consider that females are affected only if they inherit two recessive alleles, one from each parent, meaning they must be homozygous recessive. This frequency is q^2, or approximately (0.316)^2 = 0.1, which gives us about 1 in 100, so the correct answer is B: 1 in 100 affected females.