“All In The Family” Pedigree Analysis

What is a pedigree? Pedigree charts show a record of the family of an individual. They can be used to study the transmission of a hereditary condition. Useful when there are large families and a good family record over several generations.

Why use one? It is a Key Tool in Human Genetics It is like puzzle-building – you try assigning potential genotypes until the pieces fit

Symbols Used Normal male Affected male Normal female Affected female Marriage A marriage with five children, two daughters and three sons. The middle son is affected by the condition. Eldest child  Youngest child

People who have children together are connected by a horizontal line: Their children are connected to them with a vertical line. Siblings are connected as shown.

Organizing a Pedigree Chart –Generations are identified by Roman numerals I II III IV

And more organizing… Individuals in each generation are identified by Arabic numerals numbered from the left Therefore the affected individuals are II3, IV2 and IV3 I II III IV

Patterns of recessive traits may appear to “skip” generations most children of normal and affected parents are normal –AA x aa ---> Aa all children of two affected parents will be affected –aa x aa ---> aa

A Pedigree of a Recessive Human Trait Note: Trait can appear in offspring of parents without the trait. Heterozygotes who do not show the trait are termed carriers.

Patterns of dominant traits at least one parent must be affected in order for children to be affected –Aa x aa normal parents will always produce normal offspring –aa x aa ---> aa

A Pedigree of a Dominant Human Trait Note: Trait appears in every gen. and ½ the offspring of an affected heterozygote are expected to show the trait.

So, let’s practice… Background: PKU is a recessive disease where sufferers lack a protein needed to properly digest foods. It can be fatal if untreated.

In EduCreations… Key H = healthy h = PKU 1) Manny and Rosa are married and both are healthy. 2) They have 3 children. 3) Their oldest child, Jacob, has a recessive disorder called PKU. 4) Their middle child Erica and their youngest Matthew are healthy. Hint: Fill in what you know first!

If only it was that simple! The next generation… Key H = healthy h = PKU 5. Erica meets Moe at college and they get married. 6. Erica and Moe have 2 daughters. 7. Their youngest daughter Jamie shows signs of PKU while Amy does not. Fill in the genotypes of the four individuals. (start with what you know)

Sickle cell anemia (recessive) pedigree hh Key H = Healthy h = Sickle cell disease Hint: 3 unknown Start with the shaded circles and squares. They must be hh because they have the disease.

Sickle cell anemia (recessive) pedigree hh H HHHH HHH H Key H = Healthy h = Sickle cell disease Hint: 3 unknown Everyone else is healthy so they have at least one capital H.

Sickle cell anemia (recessive) pedigree hh H HHHH HHH H Key H = Healthy h = Sickle cell disease Hint: 3 unknown George must be Hh because he fathered Wilma and Tom. If he was HH, none of his kids would have the disease. h