Gene regulation in prokaryotes/Review

Part A
Like the products of the lac operon, the products of the ara operon degrade a sugar so it can supply energy for the cell. From this knowledge, would you expect the ara to be repressible or inducible? Explain

Part B
AraC is required both as an activator and a repressor. Which activity is favored in the presence of arabinose? Explain.

Part C
When araC mutants were first anaylzed, people concluded that AraC protein acts as an activator, not a repressor. Explain why they came to this conclusion.

Part D
What effect, if any would be the effect of deleting the araO2 sites where AraC binds?

Part E
Explain how the presence of glucose will affect expression of the ara operon. Be specific!

Part A
For each of the E. coli diploids that follow, indicate whether the strain is inducible, constitutive or negative for β-galactosidase and permease.

i-o+z-y+/i-ocz+y-

i+o+z+y+/i-ocz+y-

Part B
Suppose you have isolated a Lac- mutant and by genetic analysis have found that the cell is z+y+; you have also found that the mutation, which you call i*, is in the i gene. The diploid i*o+z+y+/i-o+z+y+ is constructed and found to be Lac-

Is i* dominant or recessive?

The diploid i*o+z+y+/i+ocz+y+ is Lac+. Suggest a property of the mutant repressor that would explain this phenotype. Explain your answer.

Would i*o+z+y+/i+ocz-y+ make β-galactosidase? Explain.