Identifying carriers in a recessive pedigree Steps:

• Locate affected individuals: they must be homozygous recessive (aa) and show the disease.
• Note unaffected parents of affected offspring: for a recessive trait, both must be heterozygous (Aa) to produce aa children.
• Examine unaffected individuals without affected descendants: they could be AA or Aa, but lack evidence for Aa.
• Confirm heterozygotes only where inheritance patterns require carriers (e.g., unaffected with aa child).

Why A is correct:

• Members 5 and 7 are unaffected but have an affected child, so both must carry the recessive allele (Aa) per Mendelian recessive inheritance.

Why the others are wrong:

• B (3 and 6): 3 is likely affected (aa), not heterozygous; 6 lacks carrier evidence.
• C (2 and 5): 2 is homozygous dominant (AA) as unaffected without affected offspring; 5 is heterozygous but paired wrongly.
• D (1 and 4): Both are unaffected grandparents without direct affected descendants, so possibly AA, not confirmed Aa.

Final answer: A