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PEDIGREE CHARTS

PEDIGREE CHARTS. A family history of a genetic condition. Pages 1-3 & 6-9 taken from Paul Billiet at the following website: saburchill.com /IBbiology/ ... /images/05 PEDIGREE CHARTS.ppt. What is a pedigree chart?. Pedigree charts show a record of the family of an individual

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PEDIGREE CHARTS

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  1. PEDIGREE CHARTS 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. 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 Arabic numerals numbered from the left • Therefore the affected individuals are II3, IV2 and IV3

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

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