In biology, a pedigree is a diagram showing genetic relationships between members of a family. It is used to analyze patterns of inheritance for specific genetic traits.
Analyzing a pedigree often allows determination of how a specific trait is passed down among members of a family. This analysis is useful in identifying potential risks for future offspring and the possibility of current members of the family developing a disease in the future. Pedigrees are also used by researchers attempting to identify specific genes causing human genetic disorders.
The traditional symbol used for a male in pedigrees is a square shape. Females are represented by circles. A horizontal line drawn between the two symbols represents a marriage, with vertical lines dropping down from the couple representing the presence of children. Shapes that are shaded represent individuals that exhibit the studied genetic trait.
Each individual on a pedigree inherits two genetic instructions for each trait. One instruction is inherited from the mother, and one instruction is inherited from the father. These genetic instructions are called alleles. The inherited alleles may contain the same instructions, or the instructions may differ. Alleles containing the same instructions are called homozygous alleles, whereas alleles containing different instructions are called heterozygous alleles.