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Pedigree Charts The family tree of genetics. What is a Pedigree?  A pedigree is a flow chart that uses symbols to show the genetic history of family.

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Presentation on theme: "Pedigree Charts The family tree of genetics. What is a Pedigree?  A pedigree is a flow chart that uses symbols to show the genetic history of family."— Presentation transcript:

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

12

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


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