Genetic Pedigrees

A pedigree is a chart for tracing genes in a family. Phenotypes are used to infer genotypes on a pedigree. Autosomal genes show different patterns on a pedigree than sex-linked genes. Ex:

Creating a pedigree Okay, here are some general rules to keep in mind when creating a pedigree: = females = males / = certain trait or disorder is expressed. Circles/squares are half shaded or dotted to represent carriers (heterozygous individuals). Note: Carriers of recessive diseases/disorders are considered HEALTHY and don’t express the disease or disorder. So, often, when someone is healthy, we don’t know if they’re homozygous or heterozygous. Unless, of course, the disease/disorder is dominant.

Creating a pedigree (cont.) Let’s try an example (create your pedigree on a separate sheet of paper [for practice], following these instructions; you only have to include the actual drawing): Trace the Ramirez family history of PKU (phenylketonuria), which is a recessive genetic disorder (healthy is dominant). Lets start with a key: H = Healthy h = PKU

Creating a pedigree (cont.) 2. Manny and Rosa are married and both are healthy.

Creating a pedigree (cont.) 3. They have 3 children. 4. Their oldest child, Jacob, has a recessive disorder called PKU.

Creating a pedigree (cont.) 5. Their middle child Erica and their youngest Matthew are healthy. 6. Now, If healthy is dominant to PKU, fill in the missing genotypes. (start with what you know).

Creating a pedigree (cont.) We know Jacob has PKU, so he is hh. Now, work backwards for the rest… If Jacob is hh, then he has to have gotten one of each allele from each parent. hh H h H Since Manny and Rosa are healthy, it is safe to say they are heterozygous. h hh

Creating a pedigree (cont.) By finishing the punnett sqaure, we know that the other 2 children could be either homozygous dominant or heterozygous. You should have something like this… H h H HH Hh H h H h h Hh hh hh H ? H ?

The next generation Now lets add on to this… 7. Erica meets Moe in college and the two become married (add to your pedigree). 8. Erica and Moe have 2 daughters (add this to your pedigree). 9. Their youngest daughter, Jaime, shows signs of PKU, while Aimee does not (add to pedigree). 10. Fill in the genotypes of the four individuals…starting with what you know.

This is what you should have! Woo-hoo! The Next Generation Key H = Healthy h = PKU H h H h H ? hh This is what you should have! Woo-hoo! (Mrs. Moore)

Sickle cell anemia (recessive) pedigree Use the key and fill out this pedigree Hint: 3 unknown Key H = Healthy h = Sickle cell anemia

You should have something that looks like this… Hh hh H? hh Hh hh Hh Hh hh Hh Hh H? Key H = Healthy h = Sickle cell anemia H?