1. A family history of a genetic condition or trait
PEDIGREE CHARTS
A family history of a genetic condition or trait

2. What is a pedigree chart?
Pedigree charts show a record of the family of an individual.
They can be used to study a hereditary condition or trait.
They are especially useful when there are large families that cover several generations.
© 2007 Paul Billiet ODWS

3. Studying human genetics
Today genetic engineering has new tools to offer doctors studying genetic diseases
A genetic counselor will still use pedigree charts to help determine the distribution of a disease in an affected family
© 2007 Paul Billiet ODWS

4. ORGANIZING A PEDIGREE CHART
Generations are identified by Roman numerals & are on different levels. I II
III IV

5. Males are represented by the square
Females are represented by the circle I II
III IV

6. Parents are connected with a horizontal line.
Offspring are below the parents and the bracket is connected by a vertical line.
Siblings are within the same bracket.

7. READING THE SYMBOLS USED IN PEDIGREE CHARTS
A marriage with five children, two daughters and three sons. The eldest son is affected by the condition.
Eldest child  Youngest child
Normal male
Affected male
Normal female
Affected female
Marriage
© 2007 Paul Billiet ODWS

8. Sex Linked Disorder: Color-Blindness

9. Genetic Counselors use a pedigree chart to predict the probability of transmitting an inherited disorder.
Cystic Fibrosis – autosomal recessive

10. Huntington’s Disease is autosomal dominant.

11. Hemophilia is a blood disorder that affects blood clotting
Hemophilia is a blood disorder that affects blood clotting. It comes from a recessive gene on the x-chromosome. Use the pedigree chart on worksheet to trace hemophilia through the Royal family.