Pedigree diagram illustrating the inheritance pattern of polydactyly, a dominant genetic condition in humans, with shaded symbols indicating affected individuals.

- The trait is autosomal dominant (D = dominant allele for polydactyly, d = recessive normal allele).
- Affected individuals have genotype D_ (DD or Dd); unaffected individuals have genotype dd.
- Generation I:
- Unaffected male (I-1): dd
- Affected female (I-2): Dd (must be heterozygous because she has unaffected children)
- Generation II:
- Affected male (II-2): Dd (inherited d from father I-1 and D from mother I-2)
- Unaffected female (II-3): dd
- Affected male (II-4): Dd (same reasoning as II-2)
- Unaffected female (II-5): dd (married to II-4)
- Generation III:
- Unaffected female (III-1, child of II-2 and II-3): dd
- Affected female (III-2, child of II-4 and II-5): Dd (inherited D from father II-4 and d from mother II-5)
- Affected male (III-3, child of II-4 and II-5): Dd
- Affected male (III-4, child of II-4 and II-5): Dd