What does a pedigree chart illustrate?

A pedigree chart is a visual representation that maps out the inheritance of traits within a family across generations. It typically displays family members' relationships to one another and indicates the presence or absence of specific genetic traits or conditions among those individuals. By using symbols to denote affected and unaffected individuals, a pedigree chart helps trace the lineage of a trait, illustrating how it is passed down from parents to offspring. This makes it a valuable tool in genetics for understanding heredity and predicting the likelihood of traits appearing in future generations. As such, it specifically pertains to the incidence of a genetic trait within a family, which aligns with the selected answer.