Concept explainers
Fifteen bacterial colonies growing on a complete medium are transferred to a minimal medium. Twelve of the colonies grow on minimal medium. a. Using terminology from the chapter, characterize the 12 colonies that grow on minimal medium and the 3 colonies that do not.
b. The three colonies that do not grow on minimal medium are transferred to minimal medium supplemented with the amino acid serine (min + Ser), and all three colonies grow. Characterize these three colonies.
c. The serine biosynthetic pathway is a three-step path-way in which each step is catalyzed by the enzyme product of a different gene, identified as enzymes A, B, and C in the diagram below.
Mutant 1 grows only on min
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