Polycytic kidney disease is a rare disorder affecting 1: 1250 live-born infants - HSC - SSCE Biology - Question 11 - 2002 - Paper 1

To determine the inheritance pattern of polycystic kidney disease in the pedigree provided, we analyze the family tree.

1. Observe the Affected Individuals: The affected individuals in the pedigree show that the disorder is present in both males and females, indicating it is not sex-linked.

2. Analyze the Transmission Pattern: The disease appears to pass directly from parents to children without skipping generations, which is characteristic of dominant traits.

3. Determine the Dominance: If one parent is affected, there's a significant chance their children will also be affected, which further supports the idea of a dominant inheritance.

4. Conclusion: Therefore, the best description of the inheritance mechanism of polycystic kidney disease based on the pedigree is that it is non sex-linked and dominant.