2. An E. coli strain contains the mutant alleles gal- and glu- , indicating that

Question

2. An E. coli strain contains the mutant alleles gal- and glu-, indicating that it 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. 1 pt

b. Indicate whether this strain can grow on medium containing sucrose as the only carbon source. Briefly explain your answer in the space below. 1 pt

c. Which monosaccharide would accumulate in cells grown on sucrose as the only carbon source? 0.5 pts

Explanation / Answer

2. An E. coli strain contains the mutant alleles gal- and glu-, indicating that it cannot metabolize the sugars galactose or glucose for energy.

a. No,this strain cannot grow on medium containing lactose as the only carbon source.This is because lactose being a disaccharide is broken down to glucose and galactose.The strain cannot metabolize the sugars galactose or glucose for energy so it will be unable to grow using lactose as carbon source.

b. This strain can grow on medium containing sucrose as the only carbon source.Sucrose being a disaccharide is broken down to glucose and fructose.Since the strain is unable to metabolize glucose it can survive using fructose as the carbon source.

c. Glucose would accumulate in cells grown on sucrose as the only carbon source as the strain cannot metabolize glucose.

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