What is a pedigree?

Pedigree - a diagram that maps the inheritance of a specific trait or genetic disorder through multiple generations of a family, using standard symbols (squares for males, circles for females, shaded for affected) to show relationships and phenotypes

• essentially, a family tree based on tracking a singular trait

• pedigrees are used to…

  • a) predict chances that offspring will or will not have that trait

  • b) predict chances of being a carrier (heterozygous genotype where the trait is recessive)

  • determine mode of inheritance of trait (dominant or recessive)

In this pedigree, the mother in generation one expresses the affected trait. As 2/3 of the offspring also express the trait, we can assume this is a dominant trait. As one offspring didn’t express the trait, we can also assume that the mother is heterozygous and the father is homozygous recessive, having not expressing the gene himself.