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A donor strain of bacteria with genotype leu+ gat pro+ is infected with phages. The phage lysate from the bacterial cells is collected and used to infect a second strain of bacteria that are leu- gat pro-. The second strain is selected for leu+, and the following cotransduction data are obtained:

Donor leu+ gat pro+

Recipient leu- gal+ pro~

Selected gene leu+ leu+

Cells with cotransduced gene(%)

Which genes are closest, leu and gal or leu and pro?

29. A geneticist isolates two new mutations from the rIIregion of bacteriophage T4, called rIIx and rIIy. E. coli B cells are simultaneously infected with phages carrying the rIIx mutation and with phages carrying the rIIy mutation. After the cells have lysed, samples of the phage lysate are collected. One sample is grown on E. coli K cells and a second sample on E. coli B cells. There are 8322 plaques on E. coli B and 3 plaques on E. coli K. What is the recombination frequency between these two mutations?

30. A geneticist is working with a new bacteriophage called phage Y3 that infects E. coli. He has isolated eight mutant phages that fail to produce plaques when grown on E. coli strain K. To determine whether these mutations occur at the same functional gene, he simultaneously infects E. coli K cells with paired combinations of the mutants and looks to see whether plaques are formed. He obtains the following results. (A plus sign means that plaques were formed on E. coli K; a minus sign means that no plaques were formed on E. coli K.)

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