Challenge Your Exam Readiness With Our Free ATI TEAS Practice Questions

With X-linked recessive inheritance, sons receive their Y chromosome from the father and their single X from the mother. A carrier mother (XᴺXᶜ) produces two types of eggs in equal proportions: Xᴺ and Xᶜ. A son’s genotype must be X?Y; because the father contributes Y only to sons, the determining factor is which maternal X they inherit. Half of sons receive Xᴺ (genotype XᴺY → unaffected), and half receive Xᶜ (genotype XᶜY → affected), making the probability 50% for sons specifically—answer C. Note the difference between conditional and overall child probability: if the question asked for any child being affected, you would consider sex as well (sons = 1/2 of children, affected sons = 1/2 of sons → 1/4 of all children). Daughters from this cross (Xᴺ from father + Xᴺ or Xᶜ from mother) are either XᴺXᴺ (unaffected) or XᴺXᶜ (carriers), but not affected because they would need two recessive alleles (XᶜXᶜ). TEAS genetics often tests Punnett reasoning: list parental gametes, construct outcomes, and match probabilities to the asked subset (sons vs. all children).