In an experiment similar to the Lederberg and Tatum experiment, researchers grew

Question

In an experiment similar to the Lederberg and Tatum experiment, researchers grew two strains of E. coli in complete medium Next the researchers repeated the experiment in Part C but instead of mixing the AX and AY strains, they put one strain on each side of a alass U-tube The U-tube contains a glass filter between the two strains of bacteria that prevents the cells from E. coli strain AX has the genotype Amp bio+ trp+ leu- .E. coli strain AY has the genotype Amp bio- trp- leu+ interacting directly The researchers then plated the bacteria on different media types On which type(s) of media would you expect cells from the AY side of the U-tube to grow? Select all that apply. O bio- leu- bio-trp- trp-leu- leu- trp- bio- none of the above O O

Explanation / Answer

Strain AY is bio - and trp -, meaning it cannot synthesize those (bio= biotin, a vitamin source, trp = tryptophan, an amino acid) on their own. So they can only grow in media supplemented with such. But since these molecules can cross the glass filter they can grow on the side of the tube not initially supplied with biotin and tryptophan. But they cannot grow in a leucine-deficient medium since even AX lacks the gene for it. So the answer would be bio- trp -

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