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

2. What is a pedigree chart?
Pedigree charts show a record of a specific disease or trait in a family. They can be used to study the spread of a hereditary condition
They are particularly useful when there are large families and a good family record over several generations.
Cheap and non invasive way to
investigate if a disease may be genetic
© 2007 Paul Billiet ODWS

3. Why is studying human genetics so hard?
Cannot breed humans by selection
Long time frame for each generation
Complexity of human genome
Moral/Ethical barriers
Relatively few offspring
Complex lifespan/lifestyle/epigenetic factors
© 2007 Paul Billiet ODWS

4. 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
Half-filled box is a known carrier of the trait, but not expressed (seen).
© 2007 Paul Billiet ODWS

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

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

7. Organising the pedigree chart
Individuals in each generation are identified by numerals numbered from the left to right
Therefore the affected individuals are II3, IV2 and IV3 I II
III IV
© 2007 Paul Billiet ODWS

8. Reading a Pedigree: Dominant inheritance
Gen I : Dad has the trait, mom does not.
What are the possible genotypes for mom?
Gen II : One daughter and son has the trait and one son does not.

9. A Royal Pedigree: Sex-Linked Inheritance
Gen 1: Albert and Victoria are married and do not have hemophilia
Gen 2: They have 6 children: 3 boys and 3 girls. Leopold is the only child who has hemophilia.
How do you describe generation 3 and 4?

10. Draw our own Pedigree
Widows Peak is a basic Mendelian dominant trait. A male with widows peak marries a woman who does not have widows Peak.
They have 3 children, 2 boys and 1 girl.

11. Draw our own Pedigree
We know that Color Blindness follows a Sex-Linked Recessive Pattern
Color blind dad marries a mother who can see color.
They have 3 children (2 boys, 1 color blind) and 1 color blind girl. What is the mothers genotype?
The color blind girl marries a man who can see color and they have 1 boy and 2 girls. Can their son see color? What are the possible genotypes for the girls?