This set of Vector Biology Questions & Answers for Exams focuses on “Vectors for Mammals – 5”.
1. What is reporter genes used for?
a) To confirm transformation
b) To confirm transfection
c) To induce expression
d) To cease expression
Explanation: When controlled by a strong promoter, reporter genes are often used as markers to confirm stable or transient transformation.
2. What is “CAT”?
a) Repressor gene
c) Reporter gene
d) Hybrid vector
Explanation: The first reporter gene to be used in animal cells, derived from E.coli transposons Tn9; it has also been used to a certain extent in plants.
3. The CAT gene confers antibiotic resistance.
Explanation: CAT gene encodes the enzyme chloramphenicol acetyltransferase, which confers resistance to antibiotic chloramphenicol.
4. Simian Virus 40 (SV40) is an example of ____________
c) Plant virus
Explanation: Transient transformation can be achieved using replicon vectors that contain origins of replication derived from certain viruses of the polyomavirus family such as SV40.
5. Polyomavirus vectors such as SV40 are used especially for ____________
a) Gene expression
b) Gene manipulation
c) Recombinant proteins
d) Hybrid vector production
Explanation: These viruses cause lytic infections, during the infection cycle viral gene products accumulate at high levels. Hence this strategy is used to produce recombinant proteins.
6. Which is the first virus to be developed as an animal vector?
Explanation: SV40 was the first animal virus to be characterized in detail at the molecular level and for this reason, it was also the first to be developed as a vector.
7. What is the approximate size of the SV40 vector?
a) 1 kb
b) 3 kb
c) 5 kb
d) 7 kb
Explanation: Simian Virus 40 (SV40) has a small icosahedral capsid and a circular double-stranded DNA genome of approximately 5 kb. It contains the early genes and the late genes.
8. Transcription in SV40 is controlled by ___________
a) Regulatory element
b) Late genes
c) Early genes
Explanation: Transcription in SV40 is controlled by a complex regulatory element located between the early and late regions, and this includes early and late promoters, an enhancer and the origin of replication.
9. How many proteins are produced during the first stage of SV40 infection cycle?
Explanation: During the first stage of SV40 infection cycle, the early transcript produces two proteins, known as large T and small t tumor antigens.
10. What is the function of the T-antigen of SV40 viral vectors?
a) Genome replication
Explanation: The function of T-antigen is particularly important as this protein binds to the viral origin of replication and is absolutely required for genome replication.
11. What function does an “oncoprotein” serve?
a) Controlled cell proliferation
b) Ceased cell proliferation
c) Uncontrolled cell proliferation
d) Initiates cell proliferation
Explanation: The T-antigen also acts as an oncoprotein, working with the host cell’s cycle machinery and causing uncontrolled cell proliferation.
12. Which type of infection is caused by the human BK virus?
Explanation: Human BK virus causes latent infections in which the viral genome is maintained as a low to moderate copy-number replicon that does not interfere with host cell growth.
13. An epstein-barr virus causes a latent infection.
Explanation: Epstein-Barr virus causes latent infections in which the viral genome is maintained as a low to moderate copy-number replicon that does not interfere with host cell growth.
14. What are polyadenylation signals?
Explanation: Polyadenylation signals are terminators required in eukaryotic genes to generate a defined 3’ end to the mRNA.
15. Which of the following is a source of Poly(A) sites, incorporated into mammalian vectors?
a) Mouse beta-globin
b) Bovine serum albumin
c) Maltose binding protein
Explanation: Poly-adenyl sites from the Simian 40 Virus early transcription unit or mouse beta-globin gene are often incorporated into mammalian expression vectors.
Sanfoundry Global Education & Learning Series – Vector Biology & Gene Manipulation.
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