1. A family history of genetics
PEDIGREE CHARTS
A family history of genetics
Edited from the original produced by Paul Billiet [

2. What is a pedigree chart?
a diagram that shows the appearance of a particular gene from one generation to the next
can be used to study the inheritance of a hereditary condition (like cystic fibrosis)
are particularly useful when there are large families and a good family record over several generations.

3. Symbols Used in Pedigree Charts
A marriage with five children, two daughters and three sons.
male female
Vertical lines connect children to their parents
A solid square or circle indicates that the person has a certain trait
Oldest child  Youngest child
A half-filled square or circle indicates that the person is a carrier of the trait.

4. Organizing the Pedigree Chart
A pedigree chart of a family showing 20 individuals

5. Organizing the Pedigree Chart
Generations are identified by Roman numerals I II
III IV

6. Organizing the Pedigree Chart
Individuals in each generation are identified by Arabic numerals numbered from the left I II
III IV 1 2 1 2 3 4 5 6 7 1 2 3 4 5 6 1 2 3 4 5

7. Organizing the Pedigree Chart
In this example, let’s look at a recessive trait like light eyes.
Individuals II3, II6, IV2, and IV3 have light eyes.
The carriers (of the recessive gene) are I1, I2, III5, and III6. I II
III IV 2 1 3 4 5 6 7