pedigree

A pedigree is a family tree drawn for genetics — a standardized diagram that maps how a trait travels through the generations. Squares mark males, circles mark females, horizontal lines join partners, and vertical lines drop down to their children, with shaded shapes marking who is affected.

By reading the shape of the chart, a geneticist can often deduce how a trait is inherited. A trait in every generation that affects both sexes hints at autosomal dominant; a trait that skips generations and clusters among siblings suggests autosomal recessive; one that strikes mostly males through unaffected carrier mothers points to X-linked recessive.

Pedigrees are a core tool of genetic counseling because they let one estimate the risk that a future child inherits a condition. They have limits: small families give little information, memories and diagnoses can be wrong, and confounders like reduced penetrance, new mutations, or unstated relationships can disguise the true pattern.