Pedigree Analysis

A pedigree is a systematic listing of the parents and grand parents of a given individual. It is the family tree for a large number of individuals
A pedigree chart contains different types of symbols to indicate different types of individuals and they are as follows:
1. Normal male members of a family are shown by squares and normal females by circles
2. Mating is presented by a square and a circle connected by a horizontal line


Symbols used in pedigree chart

10. Death of an individual is represented by crossing the square or circle
Different shades or colours added to the symbols can represent various phenotypes
Each generation is listed on a separate row

From the family tree given below, it is possible to find out the phenotype and genotype of three generations and they are as shown in the table

A pedigree involving an exceptional phenotype controlled by recessive allele "a" (Normally gene symbols are not given in pedigrees.

A look at the pedigree chart will given an idea about the patterns of inheritance, i.e., whether it is recessive, sex linked or autosomal

The pedigree chart for the sex linked disease-Haemophilia