Pedigree Analysis

1. Pedigree Analysis • Recognizing different patterns of inheritance within different types of pedigrees • Textbook p. 611-617

2. Tee hee

3. What is a Pedigree? • Diagram or flowchart that uses symbols to show patterns of relationships & traits in a family over many generations • 4 patterns of inheritance to be analyzed: • Autosomalrecessive • Autosomaldominant • Sex-linked recessive • Sex-linkeddominant http://media.syracuse.com/news/photo/2010/06/ugliest-dog-dies-ny114jpg-f63d008d5e193838.jpg

4. Symbols in Pedigree Charts

5. Symbols in Pedigree Charts p. 612

6. Examples http://commons.wikimedia.org/wiki/File:Pedigree-chart-example.png Dominant sex-linked Recessive autosomal Dominant autosomal Recessive sex-linked

7. Allele Notation • Dominant autosomal trait: the affected allele = “A” and the unaffected allele =“a” • Recessive autosomal trait: the affected allele = “a” and the unaffected allele = “A” • Dominant sex-linked trait: the affected allele = “XA” and the unaffected allele = “Xa” • Recessive sex-linked trait: the affected allele = “Xa” and the unaffected allele = “XA”

8. Pedigree Analysis Step 1: Determine whether the trait demonstrated by the pedigree is dominant or recessive Step 2:Determine whether the trait is sex-linked or autosomal. To do this, you must look for evidence of certain patterns of inheritance.

9. The Pedigree Decision Tree

10. Step 1: Dominant or recessive? • Use the decision tree and look for evidence!

11. Why do heterozygotes indicate a recessive trait? Heterozygote = carries the gene but does not display the trait If recessive trait, an individual with Aa will appear as this If dominant trait, an individual with Aa will appear as this: OR

12. Dominant or recessive? Recessive! Unaffected parents produce affected offspring

13. Dominant or recessive? Dominant! All affected individuals have an affected parent

14. Dominant or recessive? Recessive! Heterozygotes AND unaffected parents produce affected offspring

15. Remember the steps: Step 1: Determine whether the trait demonstrated by the pedigree is dominant or recessive • Once you do this, you are ready to go to step 2! Step 2:Determine whether the trait is sex-linked or autosomal. - The evidence you look for depends on your answer for step 1

16. The Pedigree Decision Tree

17. For recessive pedigreesStep 2: Autosomal or sex-linked? • Use the decision tree and look for evidence!

18. For recessive pedigreesStep 2: Autosomal or sex-linked? RECESSIVE AUTOSOMAL if: • Male carriers/heterozygotes • Affected female has unaffected parents RECESSIVE SEX-LINKED if: • If carrier mother x unaffected father has affected son • No affected females, suspect sex-linked

19. Example

20. 1) Recessive or Dominant?2) Autosomal or Sex-Linked? Recessive! Unaffected parents produce affected offspring Autosomal! Unaffected parents produce affected daughter

21. Example

22. 1) Recessive or Dominant?2) Autosomal or Sex-Linked? Recessive! Heterozygotes AND unaffected parents produce affected offspring Carrier mother x unaffected father producing affected sons

23. For dominant pedigreesStep 2: Autosomal or sex-linked? • Use the decision tree and look for evidence!

24. For dominant pedigreesStep 2: Autosomal or sex-linked? IF DOMINANT, the pedigree must be DOMINANT AUTOSOMAL if: • Affected father has unaffected daughter • Affected father has affected son with unaffected mother DOMINANT SEX-LINKED if: • Affected father has all affected daughters and no affected sons

25. Dominant Autosomal Pedigrees • Affected father has unaffected daughter • Affected father has affected son with unaffected mother Because father MUST be a carrier  genotype = Aa Unaffected daughter MUST be aa Since the father gives the allele to the son, it must be autosomal

26. Dominant Sex-Linked Pedigrees • Affected father has all affected daughters and no affected sons All affected daughters No affected sons

27. Example

28. 1) Recessive or Dominant?2) Autosomal or Sex-Linked? Autosomal! Affected father produces unaffected daughters Dominant! All affected individuals have an affected parent

29. Example http://commons.wikimedia.org/wiki/File:Pedigree-chart-example.png

30. 1) Recessive or Dominant?2) Autosomal or Sex-Linked? Dominant! All affected individuals have an affected parent Sex-linked! Affected fathers produce all affected daughters AND no affected sons http://commons.wikimedia.org/wiki/File:Pedigree-chart-example.png

31. The Pedigree Decision Tree

32. Genotyping

33. Genotyping

34. Pedigree Practice • Recessive or dominant trait? How can you tell? • Autosomal or sex-linked trait? How can you tell? • Identify the genotypes.

35. Pedigree Practice • Recessive or dominant trait? How can you tell? • Autosomal or sex-linked trait? How can you tell? • Identify the genotypes.

36. Pedigree Practice

37. Pedigree Practice

38. Pedigree Practice

39. Q: did you notice that the last pedigree was the same example from earlier in this lecture?!?

40. Pedigree Practice

41. Chapter 17

42. What you need to know about pedigrees: • How to be able to recognize the patterns of inheritance associated with the four types of pedigrees: dominant autosomal, dominant sex-linked, recessive autosomal, recessive sex-linked