Suppose you screened for bacterial mutants that do not metabolize lactose the op

Question

Suppose you screened for bacterial mutants that do not metabolize lactose the options below, the most likely type of mutation you have isolate Questions 22 to 25. d. a. I b. CRP ?.?" d. lacZ e. lacY Question 22. In the absence of glucose cell. , and in the presence of lactose, lactose levels remain high outside the Question 23. In the absence of both glucose and lactose, high levels of beta-galactosidase and permease are present. l tres and n he presence of lcose large amounts of lactose are found Question 24. within the cell. Question 25. In the presence of large amounts of glucose, the will metabolize lactose.

Explanation / Answer

22.Correct answer is e.lacY-

Reason:Since lactose levels remain high outside the cell in the presence of lactose, it means that lactose is not transported into the cell via enzyme permease.So, there is a mutation in lacY gene that codes for permease enzyme.

23.Correct answer is :c.Oc

Reason:Since operator is constitutively mutated,it would produce all the proteins i.e beta galactosidase and permease even in absence of lactose and glucose in medium.

24.Correct answer could be : a.Is and d.lac Z-

Reason:Since there is lactose present in the cell, it means that there is super repressor boud to operator that prevents break down of lactose via inhibition of lac Z gene expression or it may that there is mutation in lac Z gene that codes form beta galactosidase enzyme such that no lactose is broken down and hence present in the cell.

25.Correct answer is:b.CRP-

Reason:In case of mutated CRP,even if glucose levels are high, CRP forms a complex with cAMP and attaches to the CAP site which helps RNA polymerase bind to promoter,initiate transcription of lac Z gene and hence lactose is metabolied.

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