Vector Biology Objective Questions & Answers focuses on “Vectors for Mammals – 8”.
1. Why is AAV regarded as one of the safest vectors for gene therapy?
A. Lack origin
B. Helper virus dependent
A. Small sized genome
D. No toxic effects
Answer: B
Clarification: The dependence of AAV on a heterologous helper virus provides an unusual degree of control over vector replication, making AAV one of the safest vectors for use in gene therapy.
2. Where is foreign DNA inserted in an AAV virus vector?
A. Cap region
B. Rep region
A. Inverted repeats
D. Origin of replication
Answer: C
Clarification: In vitro manipulation of AAV is facilitated by cloning the inverted terminal repeats in a plasmid vector and inserting the transgene between them.
3. Which is the only element essential for replication in an AAV vector?
A. Origin of replication
B. Inverted repeats
A. Rep genes
D. Cap genes
Answer: C
Clarification: Few experiments were conducted in which both cap and rep genes were deleted and transgene was expressed from either a heterologous or endogenous promoter. It was then demonstrated that the repeats are only elements required for replication.
4. Either endogenous or homologous promoters can be used with an AAV vector.
A. True
B. False
Answer: A
Clarification: Few experiments were conducted in which both cap and rep genes were deleted and transgene was expressed from either a heterologous or endogenous promoter.
5. Deletion of which region of an AAV vector abolishes the site-specificity?
A. Origin of replication
B. Cap region
A. Rep region
D. Inverted repeats
Answer: C
Clarification: Deletion of the rep region abolishes the site specificity of proviral integration, so the vector integrates at essentially random positions.
6. Which of the following type of cells cannot be transfected by AAV vector?
A. Liver cells
B. Germ cells
A. Muscle cells
D. Neurons
Answer: B
Clarification: AAV vectors have been used to introduce genes efficiently to many cell types, including liver, muscle and neurons.
7. Use of con-catemeric replication intermediates, circumvents which of the most serious disadvantage of AAV vectors?
A. Replication ability
B. Infection cycle
A. DNA carrying capacity
D. Host range
Answer: C
Clarification: The fact that AAV uses con-catemeric replication intermediates has been used to circumvent perhaps the most serious disadvantage of AAV vectors, which is limited capacity for foreign DNA.
8. ‘Nuclear occlusion bodies’ are found in _______________
A. Baculoviruses
B. Adenovirus
A. Human somatic cells
D. Human germ cells
Answer: A
Clarification: One group of baculoviruses, known as the nuclear polyhedrosis viruses, has an unusual infection cycle that involves the production of nuclear occlusion bodies.
9. Nuclear occlusion bodies are _____________
A. Nuclear particles
B. Vitamins
A. Proteinaceous particles
D. Replication genes
Answer: C
Clarification: Nuclear occlusion bodies are proteinaceous particles in which the virions are embedded, allowing the virus to survive harsh environmental conditions such as desiccation.
10. Which protein is expressed at high levels in occlusion bodies of baculoviruses?
A. Polyhedron
B. Amylose
A. Glucose
D. Lactose
Answer: A
Clarification: The occlusion bodies are relevant to vector development because they consist predominantly of a single protein called polyhedron at very high levels.
11. The polyhedrin gene of baculovirus vectors cannot be replaced by foreign DNA.
A. True
B. False
Answer: B
Clarification: The nuclear occlusion stage of the infection cycle is non-essential for the productive infection of cell lines, thus the polyhedrin gene can be replaced.
12. AcMNPV vector is a type of __________ which is used for expression in insect cells.
A. Baculoviruses
B. Adenoviruses
A. Caulimoviruses
D. Papillomavirus
Answer: A
Clarification: Autographa californica multiple nuclear polyhedrosis virus (AcMNPV) is used for protein expression in insect cell lines, particularly those derived from Spodoptera frugiperda.
13. Bombyx mori nuclear polyhedrosis virus infects the _______
A. Drosophila
B. Plants
A. Humans
D. Silkworm
Answer: D
Clarification: BmNPV infects the silkworm and has been used for the production of recombinant protein in live silkworm larvae.
14. One limitation of baculovirus expressed system is that ___________ in mammals and insects is different.
A. Glycosylation pathway
B. Genomic size
A. Cloning efficiency
D. Virus genre
Answer: A
Clarification: One limitation of the expression system is that the glycosylation pathway in insects differs from that in mammals, so recombinant mammalian proteins may be incorrectly glycosylated and hence immunogenic.
15. Insect cell lines derived from Estigmene area have the ability of __________
A. Post-translational modification
B. Replication
A. Transduction
D. Conjugation
Answer: A
Clarification: The issue of incorrectly expressed mammalian recombinant proteins is addressed by using insect cell-lines chosen specifically for their ability to carry out mammalian-type post-translational modifications.
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