In the following pedigree, shaded individuals have a particular genetic trait - VCE - SSCE Biology - Question 7 - 2012 - Paper 1

To determine the mode of inheritance for the trait shown in the pedigree, we can analyze the pattern of inheritance:

1. Observation of the Pedigree: Notice how the shaded individuals (affected) are distributed among the generations.
2. Generation Analysis:
   • In the pedigree, there are both male and female affected individuals, suggesting that the trait may not be strictly X-linked.
   • The presence of affected females indicates that the trait could be either X-linked recessive or autosomal.
3. Transmission Patterns:
   • If the trait were X-linked dominant, every affected individual would pass the trait to all of their daughters, but affected males must also be present if this were to hold true.
   • In X-linked recessive conditions, males are typically more affected than females, which appears to be the case here. However, if we observe that the trait is appearing in both males and females across generations with equal frequency, it aligns more with autosomal traits.
4. Conclusion: Based on the distribution, the less predictable inheritance in gender ratios, and the equal expression in both sexes, the trait is most likely autosomal dominant (D).