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Published byMaximilian Lloyd Modified over 9 years ago
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Pedigree Charts The family tree of genetics
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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.
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Male Matting / Married Female Affected Offspring Identical Twins Non-identical SYMBOLS USED IN PEDIGREE CHARTS
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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.
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How many generations? How many couples? How many sisters? How many in each generation are affected? EXAMPLE:
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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:
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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.
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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
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Dominant or Recessive? AUTOSOMAL DOMINANT: Only 1 copy of the disease is needed for the disease to appear * Appears in every generation
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Dominant or Recessive? AUTOSOMAL RECESSIVE: 2 copies of the disease is needed for the disease to appear * Can skip a generation
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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
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EXAMPLE 1: Is it Autosomal or X-linked?
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Answer Autosomal DOMINANT OR RECESSIVE? Rationale: Because there are 3 females and 3 males affected
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Answer Autosomal DOMINANT - in every generation
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Example of Pedigree Charts Dominant or Recessive? Hint: Add genotypes above each individual to determine the answer
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Answer Dominant Dd dd
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Example of Pedigree Charts Dominant or Recessive?
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Answer Recessive Dd dd Dd / DDDd dd Dd dd Dd dd Dd / DD
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