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Tetrad analysis

Tetrad analysis. Fig 5.15. Nonparental = recombinant . Tetrad analysis. What if two crossovers?. Four recombinants Two recombinants No recombinants. Fig 5.15. Parental ≠ non-recombinant. Fig. 5.17. Centromere is not a mutation. But you can still use it for mapping. Fig. 5.21.

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Tetrad analysis

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  1. Tetrad analysis Fig 5.15 Nonparental = recombinant

  2. Tetrad analysis What if two crossovers? Four recombinants Two recombinants No recombinants Fig 5.15

  3. Parental ≠ non-recombinant Fig. 5.17

  4. Centromere is not a mutation But you can still use it for mapping Fig. 5.21

  5. How do we know that radiation causes genetic defects?

  6. Morgan Bridges Muller Sturtevant

  7. Muller’s X-ray experiment (1928)

  8. Muller’s X-ray experiment Created XClB

  9. Muller’s X-ray experiment Created XClB XY

  10. Muller’s X-ray experiment Created XClB •XY gametes

  11. Muller’s X-ray experiment Created XClB •XY x XClBX gametes

  12. Muller’s X-ray experiment Created XClB •XY x XClBX (Bar-eyed females) gametes

  13. Muller’s X-ray experiment Created XClB •XY x XClBX gametes •XX, •XXClB (ignore males)

  14. Muller’s X-ray experiment Created XClB •XY x XClBX gametes •XX, •XXClB

  15. Muller’s X-ray experiment Created XClB •XY x XClBX gametes •XX, •XXClB XY x •XXClB

  16. Muller’s X-ray experiment Created XClB •XY x XClBX gametes •XX, •XXClB XY x •XXClB •XY, XClBY (ignore females)

  17. Muller’s X-ray experiment Created XClB •XY x XClBX gametes •XX, •XXClB XY x •XXClB •XY, XClBY (lethal)

  18. Muller’s X-ray experiment Created XClB •XY x XClBX gametes •XX, •XXClB XY x •XXClB •XY, XClBY How many lethal mutations? (lethal)

  19. Muller’s X-ray experiment •XY, XClBY How many lethal mutations? (lethal)

  20. Muller’s X-ray experiment •XY, XClBY How many lethal mutations? (lethal) Nobel prize to Muller, 1946: “for the discovery of the production of mutations by means of X-ray irradiation”

  21. Important for radiation biology, but also for basic genetics

  22. George Beadle & Edward Tatum (1941) Do mutations affect biochemistry or only death, wing shape, pea color, etc?

  23. Bread mold Fig. 5.14

  24. Beadle & Tatum Complete med Minimal med

  25. Beadle & Tatum (why?) Complete med Minimal med

  26. Beadle & Tatum Complete med Minimal med Complete med

  27. Beadle & Tatum Complete med Minimal med Complete med Minimal med

  28. Beadle & Tatum Complete med Minimal med Complete med Minimal med Minimal + alanine

  29. Beadle & Tatum Complete med Minimal med Complete med Minimal med Minimal + serine

  30. Beadle & Tatum Complete med Minimal med Complete med Minimal med Minimal + B6

  31. Beadle & Tatum Complete med Minimal med Complete med Minimal med What’s wrong with the strain? It can use everything but B6 It can make everything but B6 It can grow on everything but B6 Minimal + B6

  32. Beadle & Tatum Complete med Minimal med Complete med Minimal med (what is a vitamin?) Minimal + B6

  33. Beadle & Tatum Complete med Minimal med Complete med Minimal med pdx strain Minimal + B6

  34. Beadle & Tatum

  35. Beadle & Tatum

  36. Beadle & Tatum Now…how many mutations cause pdx?

  37. Beadle & Tatum pdx x WT (Haploid) (Haploid)

  38. Beadle & Tatum (if single-gene, what do we expect?) pdx x WT

  39. Beadle & Tatum pdx x WT

  40. Beadle & Tatum pdx x WT

  41. Beadle & Tatum pdx x WT

  42. Beadle & Tatum pdx x WT

  43. Beadle & Tatum pdx x WT

  44. Beadle & Tatum Failure to make B6 segregates 1:1

  45. Beadle & Tatum Failure to make B6 segregates 1:1 so… mutation in a single gene

  46. Beadle & Tatum Failure to make B6 segregates 1:1 so… mutation in a single gene so… Step in B6 synthesis attributed to a single gene “One-gene-one-enzyme”

  47. Beadle & Tatum Failure to make B6 segregates 1:1 so… mutation in a single gene so… Nobel prize to Beadle & Tatum, 1958: “for their discovery that genes act by regulating definite chemical events”

  48. Beadle & Tatum Not quite one-gene-one-enzyme: Fig. 9.1 “One-gene-one-polypeptide”

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