An E. coli strain carries mutations in the genes responsible for metabolizing ga

Question

An E. coli strain carries mutations in the genes responsible for metabolizing galactose and glucose (gal- and glu-) Cells that carry mutations in these genes cannot metabolize the sugars galactose or glucose for energy. a. Indicate whether this strain can grow on medium containing lactose as the only carbon source. Briefly explain your answer in the space below. b. Indicate whether this strain can grow on medium containing sucrose as the only carbon source. Briefly explain your answer in the space below. c. Which monosaccharide would accumulate in cells grown on sucrose as the only carbon source?

Explanation / Answer

Answer:

3. (a) This mutant strain of E. coli cannot grow on medium containing lactose as the sole carbon sourse. Lactose is a disaccharide made up of glucose and galactose. Since the mutant cannot metabolize glucose and galactose, it cannot grow in this medium.

(b) This strain would grow in a medium containing sucrose as the only carbon source. Sucrose is a disaccharide containing glucose and fructose. Since the bacteria can metabolize fructose, it will be able to grow.

(c) Since the cells cannot metabolize glucose, the cells are expected to accumulate glucose when grown on sucrose as the only carbon source.

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