Vector Biology Questions and Answers for Aptitude test focuses on “Vectors for Mammals – 10”.
1. Retroviral vectors can be used to make stably transformed cell lines because____________
A. Cloning efficiency
B. Stable transformation
A. No host lysis
D. Cost efficiency
Answer: C
Clarification: Retroviruses do not kill the host, but produce progeny virions over an indefinite period, they can be used to make stably transformed cell lines.
2. Viral gene expression is driven by weak promoters.
A. True
B. False
Answer: B
Clarification: Viral gene expression is driven by strong promoters, which can be subverted to control the expression of transgenes.
3. MLV is a type of __________ vector.
A. Bacteriophage
B. Retrovirus
A. Hybrid
D. Agrobacterium
Answer: B
Clarification: Some retroviruses such as amphotropic strains of murine leukemia virus (MLV) have a broad host range allowing the transduction of many cell types.
4. Retroviruses make efficient and convenient vectors for gene transfer because ___________________
A. Genome is large
B. Genome is small
A. Broad host range
D. Cost efficiency
Answer: B
Clarification: Retroviruses make efficient and convenient vectors for gene transfer because the genome is small enough for DNA copies to be manipulated in vitro.
5. The major disadvantage of oncoretroviral vectors is that they infect only ___________
A. Dividing cells
B. Non-dividing cells
A. Plant cells
D. Bacterial cells
Answer: A
Clarification: The major disadvantage of oncoretroviral vectors is that they only productively infect non-dividing cells, which limits their use for gene-therapy applications.
6. HIV retroviruses infect which type of cells?
A. Germ cells
B. Non-dividing cells
A. Dividing cells
D. Cancer cells
Answer: C
Clarification: Lentiviruses such as HIV are complex retroviruses that have the ability to infect non-dividing cells. These were initially developed as vectors for the stable transduction of cells displaying CD4.
7. How many copies of the RNA genome is contained in the capsid of a retrovirus?
A. 1
B. 2
A. 3
D. 4
Answer: B
Clarification: The capsid contains two copies of the RNA genome, as well as reverse transcriptase/integrase. Immediately after infection, the RNA genome is reverse transcribed.
8. How many genes does the integrated provirus contain?
A. 1
B. 2
A. 3
D. 4
Answer: C
Clarification: The DNA intermediate integrates into the genome at an essentially random site. The integrated provirus contains three genes.
9. The _______ gene of the integrated provirus codes for viral envelope protein.
A. Gag
B. Env
A. Pol
D. LTR
Answer: B
Clarification: The integrated provirus contains three genes. The env gene encodes for viral envelope proteins and the other two for various other proteins.
10. Viral genomic RNA is synthesized by ___________
A. Gag, pol, env
B. Long terminal repeats (LTR)
A. Reverse transcriptase
D. Single promoter
Answer: B
Clarification: Viral genomic RNA is synthesized by transcription from a single promoter located in the left LTR and ends at a polyadenylation site in the right LTR.
11. The genomic RNA is capped and polyadenylated, allowing the ____ gene to be translated.
A. Gag
B. Pol
A. Env
D. Transcriptase
Answer: A
Clarification: The genomic RNA is capped and polyadenylated, allowing the gag gene to be translated, producing fusion proteins that are later processed into several distinct polypeptides.
12. Full-length RNA undergoes splicing allowing _______ gene to be translated.
A. Integrase
B. Env
A. Transcriptase
D. Pol
Answer: B
Clarification: Some of the full-length RNA undergoes splicing, eliminating the gag and pol genes and allowing the downstream env gene to be translated.
13. What is required for RNA genome to be incorporated into the capsid?
A. Cis-acting elements
B. Trans-acting elements
A. Integrase
D. RNA polymerase
Answer: A
Clarification: Two copies of full-length RNA genome are incorporated into each capsid, which requires a specific cis-acting packaging site.
14. Retroviral vectors are replication defective.
A. True
B. False
Answer: A
Clarification: Most retroviral vectors are replication-defective because removal of the viral genes provides the maximum capacity for foreign DNA.
15. The inclusion of gag-coding region improves packaging efficiency by ________
A. 2 fold
B. 6 fold
A. 8 fold
D. 10 fold
Answer: D
Clarification: The inclusion of a small portion of gag-coding region improves packaging efficiency by 10 folds. Deleted vectors can only be propagated using the helper virus.
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