Lecture 12 - Bacterial genetic maps

Lecture 12 - Bacterial genetic maps - Lecture 12 Bacterial...

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Lecture 12 – Bacterial Genetic Maps Reconstructing Lederberg’s observation: Strain A Strain A Strain B Strain B + met bio thr + leu thi 100,000,000 cells/plate Minimal Medium (MM) On MM, only recombinant can grow. Minimal Medium (MM) + Methionine +Biotin + Threonine + Leucine +Thiamine
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rare Hfr cell
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thr E. coli chromosome leu met + bio thi (crossovers) chromosome Strain B (F ) F Strain A (Hfr) Rare Hfr genetic recombination
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Few cells are donors for genetic recombination. Strain A (F + ) Strain B (F ) Hfr most cells F + { …20 to 30 integration sites ~1/100,000 cells F F HfrA HfrB Strain B (F + ) Strain A (Hfr) Strain B (F ) Strain B (F ) Exconjugants:
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Cross Exconjugant Recombination F + x F F + low frequency Hfr x F F high frequency Mating Outcome All markers transferred equally at ~1 in 10,000,000 cells. Markers transferred in specific order at ~1 in 1,000 to 10,000 cells.
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Hfr state and Hfr strain Hfr strains were identified because, in essence, the F plasmid got stuck in the integrated Hfr state. Once recombination between the F plasmid and the host chromosome occurs, the cell is in an Hfr state. A plasmid that can reversibly integrate into the host chromosome is called an episome.
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Bacterial Mating Strain A Strain B Hfr str S aux +
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This note was uploaded on 07/08/2009 for the course LIFESCI ls 4 taught by Professor Merriam during the Winter '08 term at UCLA.

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Lecture 12 - Bacterial genetic maps - Lecture 12 Bacterial...

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