Pedigrees Who do we inherit our traits from? DO YOU LOOK LIKE YOUR AUNT OR UNCLE? DO YOU AND YOUR COUSIN SHARE TRAITS?

Pedigrees Overview I. What is a pedigree? A. Definition B. Uses II.Constructing a pedigree A.Symbols B. Connecting the symbols III. Interpreting a pedigree

Pedigree definition & uses A pedigree is a chart of the genetic history of family over several generations. They show: 1) How traits are transmitted (causes of diseases) 2) Predictions of the probabilities of having an affected child 3) If the trait is dominant or recessive 4) If the gene is autosomal or X-linked

Pedigree Construction

Pedigree Example

Interpreting a Pedigree Chart Determine whether the disorder is dominant or recessive. If the disorder is dominant, one of the parents must have the disorder. If the disorder is recessive, neither parent has to have the disorder because they can be heterozygous.

Common Patterns AUTOSOMAL RECESSIVE INHERITANCE AUTOSOMAL DOMINANT INHERITANCE X-LINKED RECESSIVE INHERITANCE PARENT Both must be heterozygous or homozygous recessive One parent is affected There is not father to son transmission GENERATION Trait may skip generations Trait does not skip generations Trait skips generations OFFSPRING Males and females are affected equally Only half of the children are affected (males and females are affected equally) It affects more males than females

Examples of Pedigree Charts Dominant or Recessive?

Answer Dominant

Examples of Pedigree Charts Dominant or Recessive?

Answer Recessive

Pedigree Practice Being three-armed is determined by the dominant gene (T). In the following pedigree, affected individuals HAVE three arms. Based on the pedigree, determine the genotype for each individual. i Ii IIi

Answer All the non-filled in males and females have to be tt. All the filled in males and females have to have a T. Number 1 must be Tt because it has an offspring that is tt. Number 7 must be Tt because it got the T from the father so it can only get t from its mother. Number 8 must be Tt because it got the T from the mother and so it can only get t from its father. Number 9 must be Tt because it got the T from the mother and so it can only get t from its father. Number 16 and 17 must be T because they got the T from their father so they can only get t from their mother. Number 4, 14, and 15 remain unknown.