Tetrad analysis Fig 5 15 Nonparental recombinant Tetrad analysis What if two crossovers Fig 5 15 A Four recombinants B Two recombinants C No recombinants Parental non recombinant Fig 5 17 Centromere is not a mutation Fig 5 21 But you can still use it for mapping How do we know that radiation causes genetic defects Bridges Sturtevant Morgan Muller Muller s X ray experiment 1928 Muller s X ray experiment Created XClB Muller s X ray experiment Created XClB XY Muller s X ray experiment Created XClB XY gametes Muller s X ray experiment Created XClB XY gametes x XClBX Muller s X ray experiment Created XClB XY gametes x XClBX Bar eyed females Muller s X ray experiment Created XClB XY x XClBX gametes XX XXClB ignore males Muller s X ray experiment Created XClB XY x XClBX gametes XX XXClB Muller s X ray experiment Created XClB XY x XClBX gametes XX XXClB XY x XXClB Muller s X ray experiment Created XClB XY x XClBX gametes XX XXClB XY x XXClB XY XClBY ignore females Muller s X ray experiment Created XClB XY x XClBX gametes XX XXClB XY x XXClB XY XClBY lethal Muller s X ray experiment Created XClB XY x XClBX gametes XX XXClB XY How many lethal mutations x XXClB XY XClBY lethal Muller s X ray experiment How many lethal mutations XY XClBY lethal Time irrad min matings with 0 males 0 0 083 24 7 3 48 11 5 Muller s X ray experiment How many lethal mutations XY XClBY lethal Time irrad min matings with 0 males 0 0 083 24 7 3 48 11 5 Nobel prize to Muller 1946 for the discovery of the production of mutations by means of X ray irradiation Important for radiation biology but also for basic genetics George Beadle Edward Tatum 1941 Do mutations affect biochemistry or only death wing shape pea color etc Bread mold Fig 5 14 Beadle Tatum Complete med Minimal med Beadle Tatum why Complete med Minimal med Beadle Tatum Complete med Complete med Minimal med Beadle Tatum Complete med Complete med Minimal med Minimal med Beadle Tatum Complete med Complete med Minimal med Minimal med Minimal alanine Beadle Tatum Complete med Complete med Minimal med Minimal med Minimal serine Beadle Tatum Complete med Complete med Minimal med Minimal med Minimal B6 Beadle Tatum Complete med Complete med Minimal med Minimal med What s wrong with the strain A It can use everything but B6 B It can make everything but B6 C It can grow on everything but B6 Minimal B6 Beadle Tatum Complete med Minimal med Complete med what is a vitamin Minimal med Minimal B6 Beadle Tatum Complete med Complete med Minimal med Minimal med pdx strain Minimal B6 Beadle Tatum Beadle Tatum Beadle Tatum Now how many mutations cause pdx Beadle Tatum Haploid pdx x WT Haploid Beadle Tatum pdx x WT if single gene what do we expect Beadle Tatum pdx x WT Beadle Tatum pdx x WT Beadle Tatum pdx x WT Beadle Tatum pdx x WT Beadle Tatum pdx x WT Beadle Tatum Failure to make B6 segregates 1 1 Beadle Tatum Failure to make B6 segregates 1 1 so mutation in a single gene 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 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 Beadle Tatum Not quite one gene one enzyme Fig 9 1 One gene one polypeptide
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