Tough Vector Biology Questions and Answers focuses on “Special Vectors for Expression in E.Coli – 3”.
1. The lambda P L promoter is a weak promoter.
A. True
B. False
Answer: B
Clarification: The lambda P L is a very strong promoter and is one of the promoters responsible for transcription of the lambda DNA molecule.
2. Lambda vector subverts which important enzyme of E.coli?
A. DNA polymerase
B. Helicase
A. RNA polymerase
D. Nuclease
Answer: C
Clarification: Lambda is a very strong promoter recognized by RNA polymerase which is subverted by lambda into transcribing phage DNA.
3. The lambda promoter is repressed by which of the following gene?
A. T gene
B. cI gene
A. Amp gene
D. Trp gene
Answer: B
Clarification: The lambda promoter is repressed by cI gene. Expression vectors that carry the lambda P L promoter are used with mutant E.coli strain.
4. Expression vectors that carry the lambda P L promoter are used with ________ E.coli strain.
A. Double
B. Hybrid
A. Mutant
D. Wild-type
Answer: C
Clarification: Expression vectors that carry the lambda P L promoter are used with a mutant E.coli host that synthesizes a temperature-sensitive form of the cI protein.
5. Below what temperature can the cI protein repress the lambda promoter?
A. 10 degrees
B. 20 degrees
A. 30 degrees
D. 40 degrees
Answer: C
Clarification: At a low temperature that is less than 30 degrees, the mutant cI protein is able to repress the lambda pL promoter.
6. At higher temperature the cI protein is __________
A. Inactivated
B. Increased
A. Decreased
D. Moderated
Answer: A
Clarification: At a low temperature that is less than 30 degrees, the mutant cI protein is able to repress the lambda pL promoter, but at higher temperatures, the protein is inactivated.
7. The T7 promoter is specific for the __________
A. Mutant strains
B. Bacteriophage
A. RNA polymerase
D. DNA polymerase
Answer: C
Clarification: The T7 promoter is specific for the RNA polymerase coded by the T7 bacteriophage. The phage RNA polymerase is much more active.
8. Gene expressed downstream of T7 promoter will be expressed at _____________
A. Low level
B. High level
A. Moderate level
D. Intermittently
Answer: B
Clarification: The phage RNA polymerase is much more active than the E.coli promoter which means that the gene inserted downstream of the promoter is expressed at a high level.
9. Which of the following is present in the lysogenic special strain of E.coli?
A. Trp promoter
B. Lac promoter
A. Ampicillin
D. IPTG
Answer: B
Clarification: A lysogen contains an inserted copy of the phage DNA in its genome. The phage DNA has been altered by placing a lac promoter.
10. How can the synthesis of T7 RNA polymerase can be switched on in a culture?
A. IPTG addition
B. IPTG removal
A. Ampicillin addition
D. Ampicillin removal
Answer: A
Clarification: Addition of IPTG to the growth medium switches on the synthesis of the T7 RNA polymerase, which in turn leads to gene activation.
11. The cassette in an expression vector comprises of ribosome binding site and ____________
A. Promoter
B. Terminator
A. Repressor
D. Inducer