Genetic Pedigrees

What is a Pedigree? A pedigree is a family tree. This tree represents genetic information of a family over several generations. A pedigree typically maps one specific disease or trait.

What does a Pedigree look like?

How do we construct a Pedigree? Basic Symbols Connecting Symbols Female Male Affected Carrier Autosomal X-linked Deceased Married Children

How do we organize a Pedigree? Each person on the pedigree is numbered from left to right, starting at the top. Each generation is indicated with a Roman numeral on the left side of the pedigree. Siblings are placed in birth order, with the oldest on the left to the youngest on the right.

I 1 2 II 2 3 4 1 III 1 2 3 IV 1 2 4 3

How do we read a Pedigree? First you have to determine if the pedigree is showing an autosomal disease or X-linked disease. Autosomal means the disease is attached to any chromosomes other than X or Y. X-linked means the disease is attached to the X chromosome. If most of the males in the pedigree are affected, the disorder is X-linked If it is a 50/50 ratio between men and women who are affected, the disorder is autosomal.

Is this Autosomal or X-linked?

Reading a Pedigree The second step is to determine whether the disorder is dominant or recessive. Dominant- One of the parents must have the disorder. Recessive- neither parent has to have the disorder because the parents can be heterozygous.

Dominant or Recessive? Recessive

Dominant or Recessive? Dominant