E6 - E1. Because there were no colonies when 109 cells of...

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E1. Because there were no colonies when 10 9 cells of the bio met phe + thr + or bio + met + phe thr strains were plated alone. E2. Mix the two strains together and then put some of them on plates containing streptomycin and some of them on plates without streptomycin. If mated colonies are present on both types of plates, then the phe + and thr + genes were transferred to the bio + met + phe thr strain. If colonies are found only on the plates that lack streptomycin, then the bio + and met + genes are being transferred to the bio met phe + thr + strain. This answer assumes a one- way transfer of genes from a donor to a recipient strain. E3. The U-tube can distinguish between conjugation and transduction because of the pore size. Since the pores are too small for the passage of bacteria, this prevents direct contact between the two bacterial strains. However, viruses can pass through the pores and infect cells on either side of the U-tube. It might be possible to use a U-tube to distinguish between transduction and transformation if a filter was used that had a pore size that was too small for viruses but large enough to allow the passage of DNA fragments. However, this might be difficult since the difference in sizes between DNA fragments and phages are relatively small compared to the differences in sizes between bacteria and phages. E4. An interrupted mating experiment is a procedure in which two bacterial strains are allowed to mate, and then the mating is interrupted at various time points. The interruption occurs by agitation of the solution in which the bacteria are found. This type of study is used to map the locations of genes. It is necessary to interrupt mating so that you can vary the time and obtain information about the order of transfer; which gene transferred first, second, etc.
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This note was uploaded on 04/07/2009 for the course BIO 325 taught by Professor Saxena during the Spring '08 term at University of Texas at Austin.

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E6 - E1. Because there were no colonies when 109 cells of...

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