Which observations in a pedigree indicate a probable autosomal-dominant (AD) trait transmission?

Question

Quizplus · Accepted Answer

Finding representation in each generation and that both males and females are affected provides strong evidence that the trait is being transmitted in an AD manner. When only males are affected, the trait is more likely to be X-linked recessive, with some women being carriers. Recessive traits tend to appear on a pedigree as "skipped generations" because carriers typically do not have the phenotype. A single affected person is more likely found with an autosomal-recessive transmission, where two unaffected carriers have mated. The trait may not appear anywhere else in the pedigree. Of course, a new mutation of an AD trait could also cause only one person to be affected, but we are looking for the most probable answer.

Which Observations in a Pedigree Indicate a Probable Autosomal-Dominant (AD)