In a pedigree analysis, a rare disease affects only males, and all daughters of an affected father are unaffected carriers while sons never inherit the trait from their father. What is the mode of inheritance?
Answer and explanation
Correct answer: C. X-linked recessive
- Step 1: Fathers pass their Y chromosome to sons and their X chromosome to daughters. Step 2. Because sons receive only Y from the father, they cannot inherit an X-linked condition from him. Daughters receive the affected X and become obligate carriers. Answer: X-linked recessive. Why not the others: Y-linked traits pass from father to all sons; autosomal dominant traits affect both sexes equally; mitochondrial traits pass from mothers.
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