Pedigree Charts

1. Pedigree Charts

2. What is a Pedigree? • Pedigree • chart of the genetic history of a family over several generations. • Since you cannot make humans of different types breed together a pedigree chart offers an ethical way of studying human genetics.

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

4. Male Female Constructing a Pedigree

5. A marriage with five children, two daughters and three sons. The middle son is affected by the condition. Eldest child  Youngest child Symbols used in pedigree charts • Normal male • Affected male • Normal female • Affected female • Marriage (mating)

6. Connecting Pedigree Symbols • Fraternal twins • Identical twins Examples of connected symbols:

7. Affected Deceased Symbols in a Pedigree Chart

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

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

10. Interpreting a Pedigree Chart • Determine if the pedigree chart shows an autosomal or (sex) X-linked disease. • If most of the males in the pedigree are affected by the disorder, then it is (sex) X-linked • If it is a 50/50 ratio between men and women the disorder is autosomal.

11. Example of Pedigree Charts • Is it Autosomal or X-linked?

12. Answer • Autosomal

13. Interpreting a Pedigree Chart • Determine whether the disorder is dominant or recessive. • If the disorder is dominant, one of the parents must have the disorder. • If the disorder is recessive, neither parent has to have the disorder because they can be heterozygous.

14. Example of Pedigree Charts • Dominant or Recessive?

15. Answer • Dominant

16. Example of Pedigree Charts • Dominant or Recessive?

17. Answer • Recessive