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Pedigrees

Pedigrees. Woof Woof. The Royal Hemophiliacs. Last class we brought up hemophilia, a disease where the blood doesn’t clot normally A famous case occurred in the Royal family. How can we trace the inheritance and predict who will be affected?. Another example: Race Horses.

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Pedigrees

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  1. Pedigrees Woof Woof

  2. The Royal Hemophiliacs • Last class we brought up hemophilia, a disease where the blood doesn’t clotnormally • A famous case occurred in the Royal family

  3. How can we trace the inheritance and predict who will be affected?

  4. Another example: Race Horses • Horse Racing is HUGE industry with lots of money at stake • Owners want to invest in a horse that will win. They will pay big money to get a horse born from a ‘winning’ dam and sire. • How can you followthe mating of several horses to determinewhich horses will make a prize-winning foal?

  5. A Pedigree is a chart that traces the inheritance of a trait amongst members of a family • It shows ancestry, and is often usedto look at the inheritance of a particulartrait, often a disease • It is used to breed plants and animalsto optimize ‘good traits’ and lose ‘bad’traits

  6. The Basics of a Pedigree • Each person is represented by a symbol • Birth order is from left to right (oldest youngest)

  7. How are we related? I 1 2 II 1 2 3 4 5 6 7 8 III 1 2 3 4 5 6 7 8 9

  8. 4 Main types of Inheritance • Autosomal Dominant • Autosomal Recessive • Sex-Linked Dominant • Sex Linked Recessive Also, holandric (Y-linked), and diseases can be sporadic (not genetic) But how can we use a pedigree to figure out inheritance?

  9. How can we use a pedigree to understand inheritance • Use our knowledge of genetics and Punnett Squares • i.e What is the genotype of II-1if he expresses an autosomalrecessive disorder for the gene‘r’? • What are his parents genotypes? • What possible genotypes doeshis sister have?

  10. If I-2 is a carrier for male pattern baldness, what do we expect to be the phenotype of her children?

  11. Determining Genotype • What are the genotypes of all the individuals listed if the mutation for colourblindness is inherited in a sex-linked recessive manner? XbY XBXB XBY XBY XBY XBXb XbY XBY

  12. Patterns of Inheritance

  13. Autosomal Dominant • Affected individuals have one affected allele and one normal allele • Each offspring has a 50% chance of inheriting the mutant gene

  14. Autosomal Recessive • Affected only when have TWO copies of the mutant gene • 1 mutant copy/1 normal = carrier • Females and males are equally affected

  15. Autosomal Recessive • When 2 carriers mate: • 25% homozygous unaffected, • 50% carriers, 25% affected

  16. X-Linked Recessive • All females who have it are carriers but look normal • All males who have it are affected • No father to son transmission but if a father is affected, his daughter will be a carrier

  17. X-linked Dominant • No father to son transmission • All of an affected man’s daughters will be affected • 50% of an affected woman’s children will be affected

  18. What mode of inheritance? Autosomal Dominant!

  19. Assemble and interpret the pedigrees • Each table group is given a sheet that outlines some of the individuals in a family • Draw a proper pedigree on chart paper • Determine the mode of inheritance • Determine the phenotype/genotype of several individuals

  20. Your Pedigree must have: • Generation numbers • Individual numbers • Affected/Deceased/Carriers are marked • For this example, I also want you to include the genotype of each person once you figure out the mode of inheritance

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