1. A family history of a genetic condition Pages 1-3 & 6-9 taken from Paul Billiet at the following website: saburchill.com/IBbiology/.../images/05PEDIGREE CHARTS.ppt

2. What is a pedigree chart? Pedigree charts show a record of the family of an individual 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.

3. Studying human genetics You cannot make humans of different types breed together Pedigree charts offer an ethical way of studying human genetics Today genetic engineering has new tools to offer doctors studying genetic diseases A genetic counsellor will still use pedigree charts to help determine the distribution of a disease in an affected family

4. Sex on a Pedigree Males Females

5. Connecting Lines Marriage – horizontal line between two people Siblings – horizontal line above boxes Twins Fraternal Identical Children are listed from youngest to oldest (left to right)

6. Symbols used in pedigree charts Normal male Affected male Normal female Affected female or autosomal carrier (heterozygote ) x-linked carrier or deceased

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

8. Organizing the pedigree chart Generations are identified by Roman numerals I II III IV

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

10. Reading a Pedigree Chart Autosomal or x-linked trait? If the affected are mostly males then the trait is x-linked If the affected is a fairly even ratio between males and females then the trait is autosomal

11. Autosomal or X-linked?

12. Autosomal

13. Determining Dominant or Recessive Trait? If the disorder is dominant one of the parents must have the disorder If the disorder is recessive then neither of the parents HAS to have the trait because they are heterozygous. However one of both may have the disorder

14. Dominant or recessive?

15. Dominant

16. Dominant or Recessive?

17. Recessive Some times carriers are not listed as a half filled in square/circle. You must interpret the pedigree

18. Remember…. you must READ and INTERPRET the pedigree.