1. PEDIGREES

2. What is a pedigree chart?
Chart that shows inheritance of a trait from one generation to the next.
= male
= female

3. Symbols used in pedigree charts
Normal male
Affected male
Normal female
Affected female
Marriage (breeding couple)
Vertical line connects parents
to children

4. A marriage with five children, two daughters and three sons
A marriage with five children, two daughters and three sons. The third eldest child (a son) is affected by the condition.

5. Organizing the pedigree chart
A pedigree chart of a family showing 20 individuals

6. Organising the pedigree chart
Generations are identified by Roman numerals I II
III IV

7. Organizing the pedigree chart
Individuals in each generation are identified by Arabic numerals numbered from the left (birth order)
Therefore the affected individuals are II3, IV2 and IV3 I II
III IV

8. Guidelines
If trait skips a generation (no shading), it most likely is recessive
If trait appears every generation (shading), it is most likely dominant
If trait affects males and females equally, it is most likely autosomal

9. Guidelines (X-Linked)
If trait affects males more than females, it is X-Linked
Females tend to “carry” traits and affect their sons
If daughter has trait, her father is affected and her mother is affected/carrier
Affected sons get traits from their mother and will give trait to their daughter to “carry”