A pedigree tree is a diagram depicting members of a family, their inter-relations, and their disease or phenotypic status. It provides an overview of the inheritance pattern and frequency of a specific trait.

Each family member is represented by a symbol: circles for females and squares for males. Filled symbols represent affected individuals, and empty ones represent normal individuals. Matings are illustrated by connecting horizontal lines, while their offspring is depicted beneath. Each generation is assigned a Roman number (e.g. I, II, III) while individuals of a generation are assigned Arabic numbers (e.g. 1, 2, 3).

A pedigree tree showing 3 generations of a family and their status for a genetic condition. Squares represent males and circles represent females, with a blank shape indicating an unaffected individual and a filled shape representing an affected individual. Generation one is labelled with a roman numeral one and contains two individuals. Individual one is represented by a filled square. Individual two is represented by a blank circle. A horizontal line connects individuals one and two. A vertical line descends from this horizontal line, and branches connect to their offspring in generation 2. Generation 2 contains 6 individuals, 3 are offspring from the generation one pair and 3 are unrelated. Individual one in generation two is shown as a blank square and is not descended fro the parents in generation one. Individual 2 is depicted as a blank circle and is descended from the generation one pair. Individuals one and two are connected by a horizontal line, indicating a pairing. Next, individual 3 is depicted as a blank square, and is descended from the generation one pair. A horizontal line connects individual 3 to individual 4, who is a blank circle and not related to the generation one pair. Individual 5 is shown as a blank circle descended from the generation one pair. A horizontal line connects individual 5 to individual 6, who is a blank square with no relation to the generation one pair. In generation three, the offspring of the generation 2 pairs are shown. Each generation 2 pair has 2 offspring, so there are a total of 6 individuals in generation 3. Individuals 1 and 2 in generation 2 are the parents of individuals one and 2 in generation 3, as indicating by lines extending down from the pair. Individual 1 in generation 3 is a blank circle. Individual 2 is a filled square, or affected male. Individuals 3 and 4 in generation 3 are descended from 3 and 4 in generation 2. Individual 3 is a blank circle. Individual 4 is a blank square. Individuals 5 and 6 in generation 3 are the offspring of individuals 5 and 6 in generation 2. Individual 5 is a blank circle and individual 6 is a blank square.