This set of Vector Biology Quiz focuses on “Special Vectors for Expression in E.Coli – 2”.
1. What is the most critical component of an expression vector?
Explanation: The promoter is the most important component of an expression vector because it controls the very first stage of gene expression.
2. The rate at which messenger RNA is synthesized is determined by ______________
Explanation: The promoter controls the attachment of RNA polymerase enzyme to the DNA and determines the rate at which messenger RNA is synthesized.
3. The amount of recombinant protein obtained depends on the nature of nature of host.
Explanation: The amount of recombinant protein obtained depends on the nature of nature of the promoter. The promoter controls the attachment of RNA polymerase enzyme to the DNA and determines the rate at which messenger RNA is synthesized.
4. A small variation in the consensus sequence of a promoter will lead to change in the variation of ______________
a) Efficiency of transcription
b) Translational efficiency
c) Cloning efficiency
d) Host range
Explanation: Although most E.coli promoters do not differ much from the consensus sequences, a small variation may have a major effect on the efficiency with which the promoter can direct transcription.
5. For genes whose products are needed in small amounts, which types of promoters are required?
a) Strong promoters
b) Consensus promoters
c) Weak promoters
d) Any promoter
Explanation: Weak promoters are inefficient, direct transcription of genes whose products are needed in only small amounts.
6. Strong promoters sustain a _______ rate of transcription.
a) Medium rate
b) Low rate
c) High rate
d) Average rate
Explanation: Strong promoters are those that can sustain a high rate of transcription; strong promoters usually control genes whose translational products are required in large amounts by the cell.
7. Induction and repression are types of ___________
Explanation: An important factor to be considered during construction of an expression vector is that whether it will be possible to regulate the promoter.
8. An inducible gene is the one whose __________ can be switched on by the addition of a chemical to the medium.
Explanation: An inducible gene is the one whose transcription can be switched on by the addition of a chemical to the medium, which is a substrate.
9. A repressible gene is the one that can be _________
a) Switched off
b) Switched on
Explanation: A repressible gene is switched off by the addition of the regulatory chemical. This chemical is one of the substrates for the enzymes.
10. High level of transcription may affect the ability of the recombinant plasmid to _____________
d) Take up DNA
Explanation: Regulation of the cloned gene is desirable, as a continuously high level of transcription may affect the ability of the recombinant plasmid to replicate, leading to its eventual loss from the culture.
11. The “tac promoter” is induced by _______
Explanation: The “tac promoter” is a hybrid between the trp and lac promoters. It is stronger than either but still induced by IPTG.
12. The “lac promoter” is the sequence that controls transcription of _____________
a) LacZ’ gene
b) Trp gene
c) Lambda DNA
Explanation: The “lac promoter” is the sequence that controls transcription of LacZ’ gene, coding for beta-galactosidase.
13. Tryptophan synthesis is controlled by _________
a) Lac promoter
b) Trp promoter
c) Tac promoter
d) Lambda promoter
Explanation: The trp promoter is normally upstream of the cluster of genes coding for several of the enzymes involved in the biosynthesis of the amino acid tryptophan.
14. The lac promoter is induced by _____
Explanation: The lac promoter is induced by isopropylthiogalactosidase (IPTG), so an addition of a gene inserted downstream of the lac promoter.
15. Lambda P L promoter is responsible for the transcription of ____________
a) Lambda DNA
b) Lambda RNA
Explanation: Lambda P L promoter is responsible for the transcription of lambda DNA. It is a very strong promoter recognized by a polymerase.
Sanfoundry Global Education & Learning Series – Vector Biology & Gene Manipulation.
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