Recessive Inheritance in Pedigrees

Steps:

• Identify affected individuals (shaded symbols) as homozygous recessive (aa).
• Trace unaffected parents of affected children as carriers (Aa), since they must carry the recessive allele.
• Analyze unaffected siblings: they could be AA or Aa, but patterns show carrier status.
• Determine the queried genotype or probability based on 50% carrier chance for unaffected offspring of carriers.

Why C is correct:

• Option C identifies the correct carrier genotype (Aa) for the unaffected parent, per Mendel's law of segregation where two carriers produce 25% aa offspring.

Why the others are wrong:

• A assumes dominant inheritance, ignoring recessive albinism definition.
• B misidentifies homozygous dominant (AA) for a carrier parent, violating recessive transmission.
• D overestimates probability, not accounting for 50% Aa transmission from carriers.

Final answer: C