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Tetrad analysis Fig 5.15 Nonparental = recombinant.

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Presentation on theme: "Tetrad analysis Fig 5.15 Nonparental = recombinant."— Presentation transcript:

1 Tetrad analysis Fig 5.15 Nonparental = recombinant

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

3 Parental ≠ non-recombinant Fig. 5.17

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

5 How do we know that radiation causes genetic defects?

6 Bridges Muller Morgan Sturtevant

7 Muller’s X-ray experiment (1928)

8 Muller’s X-ray experiment Created X ClB

9 Muller’s X-ray experiment Created X ClB XY

10 Muller’s X-ray experiment Created X ClB XY gametes

11 Muller’s X-ray experiment Created X ClB XY x X ClB X gametes

12 Muller’s X-ray experiment Created X ClB XY x X ClB X (Bar-eyed females) gametes

13 Muller’s X-ray experiment Created X ClB XY x X ClB X XX, XX ClB (ignore males) gametes

14 Muller’s X-ray experiment Created X ClB XY x X ClB X XX, XX ClB gametes

15 Muller’s X-ray experiment Created X ClB XY x X ClB X XX, XX ClB XY x XX ClB gametes

16 Muller’s X-ray experiment Created X ClB XY x X ClB X XX, XX ClB XY x XX ClB XY, X ClB Y (ignore females) gametes

17 Muller’s X-ray experiment Created X ClB XY x X ClB X XX, XX ClB XY x XX ClB XY, X ClB Y (lethal) gametes

18 Muller’s X-ray experiment Created X ClB XY x X ClB X XX, XX ClB XY x XX ClB XY, X ClB Y (lethal) gametes How many lethal mutations?

19 Muller’s X-ray experiment Time irrad (min) % matings with 0 males 00.083 247.3 4811.5 XY, X ClB Y (lethal)How many lethal mutations?

20 Muller’s X-ray experiment Time irrad (min) % matings with 0 males 00.083 247.3 4811.5 Nobel prize to Muller, 1946: “for the discovery of the production of mutations by means of X-ray irradiation” XY, X ClB Y (lethal)How many lethal mutations?

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 medMinimal med

25 Beadle & Tatum Complete medMinimal med (why?)

26 Beadle & Tatum Complete medMinimal med Complete med

27 Beadle & Tatum Complete medMinimal med Complete medMinimal med

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

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

30 Beadle & Tatum Complete medMinimal med Complete medMinimal med Minimal + B 6

31 Beadle & Tatum Complete medMinimal med Complete medMinimal med Minimal + B 6 What’s wrong with the strain? A.It can use everything but B 6 B.It can make everything but B 6 C.It can grow on everything but B 6

32 Beadle & Tatum Complete medMinimal med Complete medMinimal med Minimal + B 6 (what is a vitamin?)

33 Beadle & Tatum Complete medMinimal med Complete medMinimal med Minimal + B 6 pdx strain

34 Beadle & Tatum

35

36 Now…how many mutations cause pdx?

37 Beadle & Tatum pdx xWT (Haploid)

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

39 Beadle & Tatum pdx xWT

40 Beadle & Tatum pdx xWT

41 Beadle & Tatum pdx xWT

42 Beadle & Tatum pdx xWT

43 Beadle & Tatum pdx xWT

44 Beadle & Tatum Failure to make B 6 segregates 1:1

45 Beadle & Tatum Failure to make B 6 segregates 1:1 mutation in a single gene so…

46 Beadle & Tatum Failure to make B 6 segregates 1:1 mutation in a single gene Step in B 6 synthesis attributed to a single gene “One-gene-one-enzyme” so…

47 Beadle & Tatum Failure to make B 6 segregates 1:1 mutation in a single gene Nobel prize to Beadle & Tatum, 1958: “for their discovery that genes act by regulating definite chemical events” so…

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


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