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How to Analyze a Pedigree

How to Analyze a Pedigree. Honors Biology Genetics!. What’s a Pedigree?. Pedigree is a family tree used to study how particular human traits are inherited. It is analyzed using logic and the Mendelian laws. Goals of a Pedigree.

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How to Analyze a Pedigree

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  1. How to Analyze a Pedigree Honors Biology Genetics!

  2. What’s a Pedigree? • Pedigree is a family tree used to study how particular human traits are inherited. • It is analyzed using logic and the Mendelian laws

  3. Goals of a Pedigree • 1. Determine the mode of inheritance: dominant, or recessive, sex-linked or autosomal • 2. Determine the probability of an affected offspring for a given cross.

  4. Basic Symbols

  5. More Symbols

  6. Dominant Pedigree? • 1. If two affected people have an unaffected child. • 2. If every affected person has an affected parent.

  7. Assigning Genotype for Dominant • 1. All unaffected are dd. • 2. Affected children of an affected parent and an unaffected parent must be heterozygous Dd, because they inherited a d allele from the unaffected parent. • 3. The affected parents of an unaffected child must be heterozygotes Dd, since they both passed a d allele to their child. (also called carriers)

  8. I 2 1 II 1 2 3 4 5 6 III 1 2 3 4 5 6 7 8 9 10 Dominant Autosomal Pedigree

  9. Recessive Pedigree? • 1. If two unaffected people have an affected child

  10. Assigning Genotype for Recessive • 1. all affected are rr. • 2. If an affected person (rr) mates with an unaffected person, any unaffected offspring must be Rr heterozygotes, because they got a r allele from their affected parent. • 3. If two unaffected mate and have an affected child, both parents must be Rr heterozygotes.

  11. Autosomal Dominant Look for: • Trait in every generation • Once leaves the pedigree does not return • Every person with the trait must have a parent with the trait • Males and females equally affected

  12. Autosomal Dominant

  13. Autosomal Recessive Look for: • Skips in generation • Unaffected parents can have affected children • Affected person must be homozygous • Males and females affected equally

  14. Autosomal Recessive

  15. Sex-Linked Dominant Look for: • More males being affected • Affected males passing onto all daughter (dominant) and none of his sons • Every affected person must have an affected parent

  16. Sex-Linked Recessive • Look for: • More males being affected • Affected female will pass onto all her sons • Affected male will pass to daughters who will be a carrier (unless mother also affected) • Unaffected father and carrier mother can produce affected sons

  17. Sex-linked recessive

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