What is a Pedigree… And Nooooo it’s not Dogfood. Biology I TCCHS

Warm Up 28 12/11-12 In typical Mendelian inheritance, a heterozygous individual exhibits the dominant trait. What is the term for when a heterozygote expresses a blend of both the dominant and the recessive trait? (ex.- blue eyes + green eyes = blue-green eyes)

Pedigree—a diagram that shows how a trait is inherited through several generations.

Human geneticists illustrate the inheritance of a gene within a family by using a pedigree chart. Squares = males Circles = females Shaded = individual has the trait or condition Unshaded = individual does not have trait or condition Horizontal line = marriage Vertical line = offspring, arranged from left to right in order of birth Roman numerals - label different generations

 = unaffected female = affected female = female carrier = unaffected male = male affected by one trait = male carrier And more...

Patterns of Inheritance By analyzing patterns of inheritance, biologists can learn about genetic diseases. If a trait is autosomal, it will appear in both sexes equally and if it is sex-linked, it is usually seen only in males. The major use of pedigree analysis is in clinical evaluation and counseling of patients with inherited abnormalities.

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

Patterns of Recessive Traits Normal parents may produce affected offspring Aa x Aa ---> 3/4 normal; 1/4 affected Affected children often result when parents are blood relatives

Patterns of Dominant Traits Trait tends to appear each generation Normal and affected individual expected to produce normal and affected children (approximate 1:1 ratio) Affected individuals generally heterozygous if rare trait Aa x aa ---> 1/2 Aa; 1/2 aa

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

It is a diagram that shows how a trait is inherited through several generations. Pedigree for the Albino Trait Pedigree for a Sex Linked Trait