This set of Vector Biology Questions and Answers for Entrance exams focuses on “Vectors for Mammals – 11”.
1. Self-inactivating vectors contain _____________
a) Suppressors
b) Deletions
c) Promoters
d) Inducers
View Answer
Explanation: Self-inactivating contains deletions in the 3’ LTR which are copied to the 5’ LTR during vector replication, thus inactivating the LTR promoter.
2. Internal promoters are intact in Self-inactivating vectors.
a) True
b) False
View Answer
Explanation: Self-inactivating contains deletions in the 3’ LTR which are copied to the 5’ LTR during vector replication, thus inactivating the LTR promoter, leaving internal promoters intact.
3. The entire expression cassette may be ____________ by DNA methylation.
a) Initiated
b) Inactivated
c) Increased
d) Decreased
View Answer
Explanation: One of the problems associated with LTR promoters is that the entire expression cassette may be inactivated by DNA methylation after a variable period of expression in the target cell.
4. Polyadenylation sites downstream of the promoter should be avoided because _______________
a) Blocking of the replication cycle
b) Elongation of RNA
c) Elongation of DNA
d) DNA synthesis is inhibited
View Answer
Explanation: Polyadenylation sites downstream of the transgene should be avoided, as these will cause truncation of the RNA, blocking the replication cycle.
5. In the construction of Retroviral vectors, __________ provides the missing viral functions.
a) Packaging line
b) Immunity line
c) Helper virus
d) Host machinery
View Answer
Explanation: Lentiviral vectors such as MLV and other viral vectors are produced by replacing viral genes with transgene and using a packaging line to provide missing viral functions.
6. EIAV vector stands for Equine _________ Anemia Virus.
a) Integrative
b) Infectious
c) Insertional
d) Initiative
View Answer
Explanation: Most interest has been shown in vectors based on HIV, bovine immunodeficiency virus (BIV) and Equine Infectious Anemia virus (EIAV).
7. How many plasmids were used for the transfection of the first generation of lentiviral packaging lines?
a) 1
b) 2
c) 3
d) 4
View Answer
Explanation: The first generation of antiviral packaging lines involved transfection of 293T cells with three plasmids containing different functional genes.
8. Which cells were transfected in the first generation of lentiviral packaging lines?
a) 293T
b) 286T
c) 393T
d) 243T
View Answer
Explanation: The first generation of antiviral packaging lines involved transfection of 293T cells with three plasmids containing different functional genes.
9. Which protein does the plasmid from VSV encode?
a) F-protein
b) A-protein
c) G-protein
d) E-protein
View Answer
Explanation: The plasmid encoding the G-protein from vesicular stomatitis virus (VSV) to replace the HIV env gene function.
10. Alphaviruses have ___________
a) Single-stranded RNA
b) Double-stranded RNA
c) Single-stranded DNA
d) Double-stranded DNA
View Answer
Explanation: The alphaviruses are a family of enveloped viruses with a single-strand positive –sense RNA genome. Examples include Sindbis virus.
11. Which of the following is an advantage of using alphaviral vectors?
a) Stable transfection
b) Transient transfection
c) Integration does not occur
d) Integration occurs each time
View Answer
Explanation: One of the advantages of using RNA viruses such as alphaviruses for gene transfer is that integration into the host genome never occurs.
12. In which part of the cell does alphavirus replication take place?
a) Cytoplasm
b) Nucleus
c) Periplasmic space
d) Matrix
View Answer
Explanation: Alphavirus replication takes place in the cytoplasm, and produces a large number of daughter genomes, allowing very high-level expression of any transgene.
13. Which of the following RNA based human viruses are extensively developed as expression vectors?
a) Baculovirus
b) Alphavirus
c) Papillomavirus
d) Bacteriophage
View Answer
Explanation: Alphaviruses are the only animal viruses with a replication cycle based solely on RNA to be extensively developed as expression vectors.
14. How many functional genes are contained in wild-type alphavirus?
a) 1
b) 2
c) 3
d) 4
View Answer
Explanation: The wild-type alphavirus contains two genes, a 5’ gene encoding viral replicase and a 3’ gene encoding a polyprotein from which the capsid structural proteins are autocatalytically derived.
15. Protein synthesis in eukaryotes is dependent on mRNAs possessing specialized 3’ cap structure.
a) True
b) False
View Answer
Explanation: Protein synthesis in eukaryotes is dependent on mRNAs possessing specialized 5’ cap structure, only the replicase gene of the alphavirus is initially translated.
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