This set of Tricky Vector Biology Questions and Answers focuses on “Vectors for Mammals – 13”.
1. What is the reason for a large genome of poxyvirus?
a) Encodes for all human genes
b) Encodes for replication machinery
c) Encodes all promoters
d) Contains a large portion of junk DNA
Explanation: The large genome and structural complexity of the virus is because it must encode and package all its own DNA replication and transcription machinery.
2. Why are recombinant genomes of poxyvirus non-infectious?
a) Virus packages its own DNA
b) Host packages viral DNA
c) DNA remains unpacked
d) Virus packages unpacked
Explanation: Since the virus normally packages its own replication and transcription enzymes, recombinant genomes introduced into cells by transfection are generally non-infectious.
3. 5-bromodeoxyuridine is an analog of ___________
Explanation: In one selection regime strategy, the transgene is inserted into the viral TK gene and negative selection using the thymidine analog 5-bromodeoxyuridine.
4. When transgene is inserted into the viral hemagglutinin locus, wild-type plaques turn ________
Explanation: When transgene is inserted into the viral hemagglutinin locus, if chicken erythrocytes are added to the plate of infected cells, wild-type plaques turn red and recombinants turn clear.
5. NEO is a type of ____________
a) Selectable marker
b) Screenable marker
Explanation: Since vaccinia vectors have a high capacity for foreign DNA, selectable markers such as NEO can be co-introduced with the experimental transgene to identify recombinants.
6. LacZ’ is a screenable marker used with Vaccinia vectors.
Explanation: Since vaccinia vectors have a high capacity for foreign DNA, screenable markers such as LacZ’ can be co-introduced with the experimental transgene to identify recombinants.
7. Transgene expression in vaccinia vectors depends on ___________
a) Exogenous promoter
b) Endogenous promoter
c) Endogenous inducer
d) Exogenous inducer
Explanation: Transgene expression usually needs to be driven by an endogenous vaccinia promoter, since transcription relies on proteins supplied by the virus.
8. Highest expression levels in Vaccinia vectors are produced by ______ promoters.
Explanation: The highest expression levels are provided by late promoters such as P11, allowing the production of up to 1 microgram of protein.
9. Vaccinia vectors cannot be used to express genes with __________
b) Junk DNA
c) Viral components
Explanation: Since the cytoplasm lacks not only host transcription factors but also the nuclear splicing apparatus, vaccinia vectors cannot be used to express genes with introns.
10. Which of the following sequence must be removed from DNA expressed in Vaccinia vectors?
Explanation: The sequence TTTTTNT must be removed from all foreign DNA sequences expressed in Vaccinia vectors since the virus uses this as a transcriptional terminator.
11. A useful binary expression system contains Vaccinia virus and bacteriophage ________
Explanation: A useful binary expression system has been developed, in which the transgene is driven by the bacteriophage T7 promoter and the T7 polymerase.
12. The vaccinia virus cannot be used to express antigens from other infectious agents.
Explanation: The vaccinia virus cannot be used to express antigens from other infectious agents by replacing the Vaccinia Tk locus with transgene encoding hepatitis B surface antigen.
13. Which cells were transfected in an early demonstration that vaccinia virus could be used to express antigens from other infectious agents?
a) Human cells
b) Insect cells
c) Plant cells
d) Monkey cells
Explanation: The transgene is cloned in a plasmid and this plasmid is then transfected into vaccinia-infected monkey cells, and recombinant vectors are then selected.
14. Vaccinia viruses expressing the influenza hemagglutinin gene were used to immunize ____________
Explanation: Vaccinia viruses expressing the influenza hemagglutinin gene are used to immunize hamsters, and induce resistance to influenza.
15. Resistance to SIV and HIV-2 was shown by infecting _______ with Vaccinia vectors.
Explanation: Monkeys infected with recombinant vaccinia and canarypox vectors have shown resistance SIV and HIV-2.
Sanfoundry Global Education & Learning Series – Vector Biology & Gene Manipulation.
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