Vector Biology Multiple Choice Questions on “Vectors for Mammals – 7”.
1. In the case of helper-dependent viral vectors, what does the helper virus contain?
A. Homeotic genes
B. Origin
A. Transposon
D. Missing genes
Answer: D
Clarification: If the insertion of transgene replaces an essential viral gene, the vector is rendered helper dependent. A helper virus is then co-introduced which carries the missing genes.
2. Usage of “packaging lines” is an alternative to __________
A. Cloning
B. Recombination
A. Co-introduction of helper virus
D. Viral vector for gene transfer
Answer: C
Clarification: An alternative to the co-introduction of helpers is to use a complementary cell line, sometimes termed as a packaging line, which is transformed with the appropriate missing genes.
3. What are amplicons?
A. Gut-less vectors
B. Hybrid vectors
A. Helper virus
D. Helper phage
Answer: A
Clarification: The amplicons are fully deleted, gutted or gutless vectors that contain just the cis-acting elements required for packaging and genome replication.
4. Which element in the amplicons is responsible for packaging?
A. Trans
B. Cis
A. Amp
D. Cysteine
Answer: B
Clarification: The amplicons are fully deleted, gutted or gutless vectors that contain just the cis-acting elements required for packaging and genome replication.
5. The advantage of “gutless vectors” is that they possess no intrinsic cytotoxic effects.
A. True
B. False
Answer: A
Clarification: The advantage of such vectors is their high capacity for foreign DNA and the fact that, since no viral gene products are made, the vector has no intrinsic cytotoxic effects.
6. Which of the following is an example of rod-shaped virus?
A. Baculovirus
B. Papillomavirus
A. Adenovirus
D. Retrovirus
Answer: A
Clarification: Rod-shaped viruses such as baculoviruses form the capsid around the genome, so there are no such size constraints.
7. Retrovirus is an example of ____________ virus.
A. Plant
B. Icosahedral
A. Hybrid
D. Binary
Answer: B
Clarification: Icosahedral virus Adenovirus and Retrovirus package their genomes into preformed capsids, whose volume defines the maximum amount of foreign DNA that can be accommodated.
8. Adenovirus vectors are useful for short-term transgene expression because _____________
A. Inefficient integration
B. Efficient integration
A. High stability
D. Small size
Answer: A
Clarification: Adenovirus vectors are suitable for transient expression in dividing cells because they do not integrate efficiently into the genome.
9. Adenovirus vectors can be used for ___________ cells such as neurons.
A. Somatic
B. Germ
A. Totipotent
D. Post-mitotic
Answer: D
Clarification: Adenovirus vectors are suitable for transient expression in dividing cells because they do not integrate efficiently into the genome, but prolonged expression can be achieved in post-mitotic cells such as neurons.
10. Adenovirus-derived vaccines have been used in humans with no reported side-effects.
A. True
B. False
Answer: A
Clarification: Adenoviruses are particularly attractive as gene therapy vectors because the virions are taken up efficiently by the cells in vivo and adeno-virus derived vaccines have been used in humans with no reported side-effects.
11. The deletion of which genes in an Adenovirus vector precludes the immunological effects?
A. E7
B. E2
A. E3
D. E4
Answer: D
Clarification: The use of E1 or E4 deletions is particularly attractive as the E4 gene is responsible for many of the immunological effects of the virus.
12. Insertion of stuffer DNA into which of the gene keeps recombination from happening?
A. E1
B. E2
A. E3
D. E4
Answer: C
Clarification: Insertion of stuffer DNA into the non-essential E3 gene can be done so that recombination yields a genome too large to be packaged.
13. Adeno-associated Virus was actually first discovered as a ___________
A. Contaminant
B. Human virus
A. Insect virus
D. Phage
Answer: A
Clarification: Adeno-associated virus (AAV) is not related to Adenovirus, but is so called because it was first discovered as a contaminant in the adenoviral state.
14. AAV is naturally __________
A. Translation defective
B. Replication defective
A. Small in size
D. Lacking attachment ability
Answer: B
Clarification: Adeno-associated virus is a single-stranded DNA virus, a member of the parvovirus family, and is naturally replication defective.
15. What happens to the AAV DNA in the absence of helper virus?
A. Does not infect the cell
B. Does not integrate
A. Integrates into host genome
D. Cannot synthesize proteins
Answer: C
Clarification: In the absence of helper virus vectors, the AAV DNA integrates into host cell’s genome, where it remains as a latent provirus.