Pedigree analysis · USMLE Step 1

Which inheritance pattern would you suspect if all children — male and female — of an affected male are affected?

  1. Autosomal dominant
  2. Autosomal recessive
  3. X-linked dominant
  4. X-linked recessive
Show answer and explanation

Correct answer: X-linked dominant

If an affected male transmits the trait to all his children (both sexes), this suggests X-linked dominant inheritance, since he passes his mutant X chromosome to all daughters and mutant Y (non-trait) to sons only, but daughters receive the trait, and if trait is fully penetrant, all children may be affected depending on pattern.

Difficulty: Medium Question 17 of 19

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