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E.Coli Strain

A nutritionally defective E.coli strain grows only on medium containing thymine, whereas another nutritionally defective strain grows only on medium containing leucine. When these two strains are grown together, a few progeny are able to grow on minimal medium with neither leucine nor thymine. How can this result be explained?

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Bacterial Conjugation

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E. coli that can only grow on medium containing thymine are called thymine auxotrophs (thy-).

E. coli that can only grow on medium containing leucine are leucine auxotrophs (leu-).

Obviously, thy- is wild-type in all other genes; therefore, they are really thy-/leu+.
Same logic applies for the leucine auxotrophs. They are really thy+/leu-.

But how can a wild-type bacteria come out of ...

Solution Summary

The solution discusses how an E.coli strain grow on a minimal medium with neither leucine nor thymine.

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