Pedigrees

What is a pedigree? A pedigree is a family tree that shows the inheritance of a trait

How do you read a pedigree? Squares represent males Circles represent females A horizontal line connecting the male and female indicates marriage Children are connected to a vertical line

An individual who is shaded in has the trait in question Each row indicates a generation Individuals in a row are numbered from left to right I II

How do you read a pedigree? Each individual is referred to by the generation number and where they are located in the row Which individuals have the trait? I II I-1 and II-2

How do you read a pedigree? Some individuals may be carriers or heterozygous for a trait These individual may be represented with a half shaded symbol; however, sometimes it is not shaded in at all

How to determine the inheritance pattern in a pedigree Dominant inheritance- –Trait appears in every generation Recessive inheritance- –Trait skips generations –Few individuals have the trait Sex-linked inheritance- –More males have the trait than females

Problem #1 Which individuals have the trait? What is the inheritance pattern? What is the possible genotype of individual II-3? I-1, II-1, II-5, II-8, III-1, III-6, III-8 dominant hh

Problem #2 Which individuals have the trait? What is the inheritance pattern? What is the possible genotype (s) of individual I-2? I-1, III-2 Recessive, sex-linked X H X H or X H X h She could be a carrier meaning she could be heterozygous and not have the trait, but she could pass it to her child

Problem #3 How do you know this is a sex-linked trait? What is the genotype of III-3? What are the chances of III-3 having a child with the trait if he marries a woman who is a carrier for the trait? Next son? More males have it than females X h Y 50%

Problem #4 What is the inheritance pattern? What is the probability of II-7 and II-8’s next child having the trait? dominant 50%