Genetic Pedigrees What is a Pedigree A pedigree

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 �Female �Male �Affected �Carrier ◦ Autosomal ◦ X-linked �Deceased �Connecting �Married �Children Symbols

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

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? Autosomal

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