PEDIGREES

It Runs In The Family! When more than one individual in a family is afflicted with a disorder, it suggests that the disorder might be inherited. A basic method for determining the inheritance of a disorder, is to look at its occurrence in several individuals within a family, spanning as many generations as possible. From the family history a genetic counselor, can draw a pedigree. A pedigree is simply a family tree that uses a particular set of standardized symbols.

Interpreting A Pedigree Chart A pedigree is a diagram that shows the phenotype of a particular genetic trait in a family from one generation to the next. Males are represented by squares and females by circles . Unshaded symbols are individuals who are not affected by the trait. Shaded symbols are individuals who are affected by the trait.

Roman numerals (I, II, III, etc.) symbolize generations. Mating Roman Numerals Arabic Numerals Roman numerals (I, II, III, etc.) symbolize generations. Each person is represented by an Arabic numeral (1,2,3, etc.). In this way, each person can be identified by the generation number and an individual number (i.e., individual II-3). A horizontal line between two symbols represents a mating . The offspring are connected to each other by a horizontal line above the symbols and to the parents by vertical lines. Children are listed in order of their births from left to right.

5 1 3 3 II-1 II-4 2 3 3 How many males? How many are affected with albinism? How many females? How many are affected with albinism? Name the individuals affected in generation II. How many matings are there? How many generations? How many children did the first couple have? How are individual I-1 and III-2 related? Grandfather & grandson I II III 1 2 1 2 3 4 1 2

The pedigree below shows the inheritance of Albinism, Write the genotypes of the individuals using (A) to represent normal skin color and (a) to represent the recessive allele (albino). I II III Aa aa 1 2 Aa A? Aa aa aa 1 2 3 4 A? Aa aa 1 2