1. PEDIGREE CHARTS
© 2007 Paul Billiet ODWS

2. Pedigree

3. A family history of a genetic condition
PEDIGREE CHARTS
A family history of a genetic condition
© 2007 Paul Billiet ODWS

4. What is a pedigree chart?
Pedigree charts show a record of the family of an individual trait/disorder
They can be used to study the transmission of a hereditary condition
They are particularly useful when there are large families and a good family record over several generations.
© 2007 Paul Billiet ODWS

5. Studying human genetics
Pedigree charts offer an ethical way of 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

6. Most common signs and symbols used in pedigree analysis

7. 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. Organizing the pedigree chart
A pedigree chart of a family showing 20 individuals
© 2007 Paul Billiet ODWS

9. Organizing the pedigree chart
Generations are identified by Roman numerals I II
III IV
© 2007 Paul Billiet ODWS

10. Organising the pedigree chart
Individuals in each generation are identified by Arabic numerals (1, 2, 3, etc.) numbered from the left
Therefore the affected individuals are II-3, IV-2 and IV-3 I II
III IV
© 2007 Paul Billiet ODWS

11. Attached Ear Lobes
If the disease was an attached earlobe than that person would have recessive information with a genotype of “ee”. They would be shaded in.
If they were not shaded in then they would have at least one E.

12. Organizing the pedigree chart
Thus, using this same chart, the person II-3 would be “ee” since they are shaded in. The parents I-1, and I-2 must be Ee and Ee in order to have a child with both “ee”. I II
III IV
© 2007 Paul Billiet ODWS

13. Huntington’s Disease Neurodegenerative genetic disorder
Mid-life onset (around 40-50)
It is much more common in people of Western European descent than in those of Asian or African ancestry
Can affect men and women
Uncontrolled body movements
Mental abilities generally decline into dementia.
Life expectancy of about 20 years after diagnosis
No cure, some treatment for symptoms

14. Dominant Trait Huntington Disease