Pedigrees A pedigree is a diagram of family relationships that uses symbols to represent people and lines to represent genetic relationships. These diagrams make it easier to visualize relationships within families.

Basic Information

Circles, squares and lines… oh my!

More Symbols

1 – Draw a pedigree for a family showing 2 parents & 4 children 1 – Draw a pedigree for a family showing 2 parents & 4 children. Make the oldest two children boys & the youngest two girls. Both parents are heterozygous for Brown eyes (B). 2 – Assume the pedigree you drew for #1 is tracing the occurrence of blue eyes in that family. Show that person II-2 has blue eyes. 3 – Using the pedigree you drew for #1, predict the genotypes of each person. Remember, blue eyes are recessive to all other colors & follow the following rules: 1 – Give any person with the trait (those shaded) 2 recessive alleles. 2 – Give everyone else (those not shaded) 1 dominant allele. 3 – Determine the genotype for each person using your knowledge of heredity.

More Interpretation Determining if the pedigree shows autosomal or X-linked disease. 1. If most of the males in the pedigree are affected, the disorder is X-linked (sex linked) 2. If it is a 50/50 ratio between men and women, the disorder is autosomal.

Autosomal or X-linked?

Autosomal – Why?

Even More Interpretation…. Determine whether the disease is dominant or recessive. If the disorder is dominant, one of the parents must have the disorder. If the disorder is recessive, neither of the parents has to have the disorder because they can be heterozygous. Recessive disorders can skip generations.

Dominant or Recessive?

Dominant – Why?