Pedigrees What is a Pedigree Pedigree a family

Pedigrees

What is a Pedigree? • Pedigree- a family record that shows how a trait is inherited over several generations • Can be used to study inherited diseases • Inheritance pattern (dominant/recessive or sex-linked/autosomal) • Predict the risk of disease in future offspring (genetic counseling)

How do we Read Pedigrees?

• On a pedigree: • A circle represents a female • A square represents a male • A horizontal line connecting a male and female represents a marriage • A vertical line and a bracket connect the parents to their children • A circle/square that is shaded means the person HAS the trait. • A circle/square that is not shaded means the person does not have the trait. • Children are placed from oldest to youngest. • A key is given to explain what the trait is.

Pedigree “Rules” • Dominant or recessive? • Dominant traits will show up in every generation • Recessive traits often skip generations • Autosomal or Sex-Linked? • Equal in males and females = autosomal • More males = X linked • Y-linked (very rare)… only males, passed from fathers to sons

Autosomal Recessive Traits • Trait is rare in pedigree • Trait often skips generations (hidden in heterozygous carriers) • Heterozygous parents will have about ¼ of kids affected • Affects males and females equally • Usually, affected kids have normal parents • If both parents are affected—all kids will be • Ex: cystic fibrosis, phenylketonuria (PKU)

Autosomal Dominant Pedigrees • Trait is common in the pedigree • Males and females equal • Affected offspring must have affected parent(s)… unless mutation • Affected individuals transmit the trait to ~1/2 of their children • Ex: achondroplasia (dwarfism), Huntington’s disease

X-linked Recessive Pedigrees • Trait is rare, skips generations • Affected fathers do not pass to their sons • Males are more often affected • Daughters of affected males are carriers • Only females will be carriers • Affected males usually born to unaffected females

Dominant or recessive? Autosomal or sex-linked?

• What is the inheritance pattern? • What are the genotypes of II 1, III-1, and III-2?

I 2 1 II 1 2 3 4 5 6 III 1 2 3 4 5 6 7 8 9 10

• Autosomal dominant

• Autosomal recessive

• Sex-linked recessive

Draw a Pedigree on your own… Tyler and Shannon (both normal) have 3 kids, Charles, Kayla, and Gary. Charles and Gary both have cystic fibrosis. Kayla does not. She marries Ben and has three kids: Phil, Heather, and Beth. Heather suffers from CF while Phil and Beth do not. Charles marries Mary and they have two kids. Their son Trey has the disorder, while their daughter Savanna does not. Trey marries Hope, who has CF, and they have Amber and Misty. Gary marries Rachel and has Dylan and Ashley has CF, while Dylan is healthy. Ashley marries Nathan, who has CF, and they have Nolan, Kameron, and Lacie. Nolan has CF and marries Emily, who is normal, and they have Madison (normal as well). Kameron falls in love with his sister, Lacie, and they have three kids (William, Garrison, and Henrietta), all of whom have CF.