This set of 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.
Explanation: 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
c) RNA polymerase
Explanation: 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
c) Amp gene
d) Trp gene
Explanation: 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.
Explanation: 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
c) 30 degrees
d) 40 degrees
Explanation: 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 __________
Explanation: 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
c) RNA polymerase
d) DNA polymerase
Explanation: 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
c) Moderate level
Explanation: 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
Explanation: 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
c) Ampicillin addition
d) Ampicillin removal
Explanation: 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 ____________
Explanation: An efficient expression vector, in addition to a strong and regulatable promoter also contains a cassette containing terminator and binding site.
12. Insertion of the foreign gene into the expression vector’s cassette fuses ____ reading frames.
Explanation: Insertion of the foreign gene into the restriction site fuses two reading frames that start with the E.coli segment and progress without a break.
13. Which type of protein is produced with cassette vectors?
a) Plant protein
b) Mammalian protein
c) Fusion protein
d) Hybrid protein
Explanation: The product of gene expression is a fusion protein, consisting of short peptide coded by the E.Coli reading frame fused to foreign protein.
14. P-terminus of the fusion protein is fused with a short peptide.
Explanation: The product of gene expression is a fusion protein, consisting of short peptide coded by the E.Coli reading frame fused to amino terminus.
15. Which of the following is responsible for the mRNA translation effectively?
a) Ribosome binding site
Explanation: Efficient translation of mRNA produced from cloned gene depends on ribosomal binding site and starting nucleotide sequence.
Sanfoundry Global Education & Learning Series – Vector Biology & Gene Manipulation.
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