1. Pedigree Charts The family tree of genetics

2. What is a Pedigree?  A pedigree is a flow chart that uses symbols to show the genetic history of family over several generations.  Genetic counsellor’s ask questions about your family history and make a pedigree chart to analyze and provide advice.

3. Male Matting / Married Female Affected Offspring Identical Twins Non-identical SYMBOLS USED IN PEDIGREE CHARTS

4. Constructing a Pedigree Each generation is shown on a different ROW Matting Couples are connected and their children are connected in between below. Children are added from left to right according to birth year.

5. How many generations? How many couples? How many sisters? How many in each generation are affected? EXAMPLE:

6. How many generations? 3 How many couples? 3 How many sets of sisters? 1 pair in generation 3 How many in each generation are affected? 2 in Gen. 2 1 in Gen. 3 EXAMPLE:

7. Uses of a Pedigree  A pedigree is a way to analyze how a trait is inherited through generations  Pedigrees help uncover the method of inheritance (ex: x-linked).  To determine the presence of absence of a particular trait, but more often the presence of a disease.

8. Inheritance Pattern  AUTOSOMAL INHERITANCE: the disease is located on a chromosome number 1-22 (not a sex chromosome)  * If there is a 50 / 50 split between males and females the disease is most likely autosomal  * if more females are affected than males

9. Dominant or Recessive?  AUTOSOMAL DOMINANT: Only 1 copy of the disease is needed for the disease to appear  * Appears in every generation

10. Dominant or Recessive?  AUTOSOMAL RECESSIVE: 2 copies of the disease is needed for the disease to appear  * Can skip a generation

11. Inheritance Pattern  X-Linked: the disease is located on the x- chromosome  - the trait appears more frequently in males because males only have 1 X chromosome.  - if a woman is affected, her dad MUST be affected

13. EXAMPLE 1: Is it Autosomal or X-linked?

14. Answer  Autosomal  DOMINANT OR RECESSIVE? Rationale: Because there are 3 females and 3 males affected

15. Answer  Autosomal  DOMINANT - in every generation

16. Example of Pedigree Charts  Dominant or Recessive? Hint: Add genotypes above each individual to determine the answer

17. Answer  Dominant Dd dd

18. Example of Pedigree Charts  Dominant or Recessive?

19. Answer  Recessive Dd dd Dd / DDDd dd Dd dd Dd dd Dd / DD