Pedigree analysis · USMLE Step 1

In pedigree analysis, which of the following features strongly suggests an autosomal recessive rather than autosomal dominant inheritance for a rare disorder?

  1. Trait appears in every generation
  2. Affected individuals always have an affected parent
  3. Unaffected parents produce rare affected children
  4. Equal number of affected males and females in every generation
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Correct answer: Unaffected parents produce rare affected children

A hallmark of autosomal recessive inheritance is that unaffected carrier parents can have affected children, even when earlier generations show no disease.

Difficulty: Medium Question 12 of 19

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