This set of Bioprocess Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Gene Therapy Using Viral Vectors”.
1. Which of the following is correct related to transgene?
a) Phenotype remains unaltered
b) Phenotype changes
c) Produced within an organism
d) Genotype changes
View Answer
Explanation: A transgene is a gene or genetic material that has been transferred naturally, or by any of a number of genetic engineering techniques from one organism to another. The introduction of a transgene (called “transgenesis”) has the potential to change the phenotype of an organism.
2. Lentivirus and Retrovirus are related.
a) True
b) False
View Answer
Explanation: Lentiviruses are a subtype of retrovirus.
3. Lentivirus and Retrovirus are not different.
a) True
b) False
View Answer
Explanation: The main difference between lentiviruses and standard retroviruses from an experimental standpoint is lentiviruses are capable of infecting non-dividing and actively dividing cell types, whereas standard retroviruses can only infect mitotically active cell types.
4. Which of the following virus is not used in gene therapy?
a) Papillomavirus
b) Retrovirus
c) Adenovirus
d) Herpes simplex virus
View Answer
Explanation: Some of the viruses currently used in gene therapy include retroviruses, adenoviruses, adeno-associated viruses and the herpes simplex virus.
5. Along with Retrovirus, Herpes simplex virus is also enveloped.
a) True
b) False
View Answer
Explanation: Animal herpes viruses all share some common properties. The structure of herpes viruses consists of a relatively large double-stranded, linear DNA genome encased within an icosahedral protein cage called the capsid, which is wrapped in a lipid bilayer called the envelope. The envelope is joined to the capsid by means of a tegument. This complete particle is known as the virion.
6. Which of the following is true for heterologous proteins?
a) It occurs naturally in the cell
b) It express the protein
c) It does not express the protein
d) It makes protein
View Answer
Explanation: In cell biology and protein biochemistry, heterologous expression means that a protein is experimentally put into a cell that does not normally make (i.e., express) that protein.
7. Endocytosis and phagocytosis are not related terms.
a) True
b) False
View Answer
Explanation: Endocytosis is a form of active transport in which a cell transports molecules (such as proteins) into the cell (endo– + cytosis) by engulfing them in an energy-using process. Endocytosis and its counterpart, exocytosis, are used by all cells because most chemical substances important to them are large polar molecules that cannot pass through the hydrophobic plasma or cell membrane by passive means. Endocytosis includes pinocytosis (cell drinking) and phagocytosis (cell eating).
8. In coated pits, the cytoplasmic surface is coated with:
a) Calcium
b) Clathrin
c) Clathrim
d) Clathrix
View Answer
Explanation: Coated pits are regions of the cell membrane specialized in receptor-mediated endocytosis. Their cytoplasmic surface is coated with a bristlelike structure made of clathrin.
9. What is the pH of early endosomes?
a) 5.0
b) 4.5
c) 6.0
d) 7.5
View Answer
Explanation: The intravesicular pH drops along the endocytic pathway, from pH 6.0–6.5 in early endosomes.
10. What is the pH of late endosomes?
a) 3.0
b) 4.5
c) 6.0
d) 7.5
View Answer
Explanation: The intravesicular pH drops along the endocytic pathway, from pH 4.5–5.5 in late endosomes and lysosomes.
11. What are lipid rafts?
a) Solid particles
b) Low concentration of cholesterol
c) Low concentration of glycosphingolipids
d) High concentration of cholesterol
View Answer
Explanation: Lipid rafts are subdomains of the plasma membrane that contain high concentrations of cholesterol and glycosphingolipids. They exist as distinct liquid-ordered regions of the membrane that are resistant to extraction with nonionic detergents.
12. The division of retrovirus is limited in invivo condition.
a) True
b) False
View Answer
Explanation: The resulting retrovirus vector can be used only with dividing cells, since cells must undergo mitosis before gene integration can occur. This feature limits in vivo use to cases such as cancer suppression but is not a limitation on ex vivo systems.
13. Which of the following virus is less affected?
a) Less mutated virus
b) Medium mutated virus
c) High mutated virus
d) Non-mutated virus
View Answer
Explanation: Viral decay acceleration (VDA) is a therapeutic strategy which increases the mutation frequency of a virus toward an error catastrophe threshold. The high mutation rate increases diversity within the viral population and facilitates survival in the face of host immune responses, depletion of target cells and antiviral therapeutics. This evolutionary advantage however comes at a considerable cost in that the vast majority of virus particles has mutated beyond a survivability threshold and is therefore non-infectious. Laboratory studies have demonstrated that therapeutics capable of increasing the mutation frequency as little as 2-fold results in collapse of the viral population. This therapeutics, termed VDA agents, accelerate the accumulation of additional mutations in the viral genome, progressively debilitating the virus which causes decay and eventual extinction of the entire viral population.
14. Proteoglycans are the survival factor of viruses.
a) True
b) False
View Answer
Explanation: The proteoglycans have very high molecular weight. If the virus is concentrated by ultrafiltration, the proteoglycan is also concentrated by nearly the same factor. While the high virus concentration would be expected to increase the number of infected cells, the presence of concentrated proteoglycan leads to increased inhibition of infection, so that the number of cells infected does not increase significantly and in some cases even decreases with the concentrated viral preparation.
15. Which of the following is correct?
a) Viral decay is not sensitive to temperature
b) Virus production is sensitive to temperature
c) Virus decay is sensitive to temperature
d) Viral production and decay increase with temperature
View Answer
Explanation: Both the rate of virus production and viral decay decrease with temperature, the rate of decay is more sensitive to temperature. Thus the amount of potentially active virus is severalfold higher when produced at 28°C. However, the transduction efficiency did not increase, presumably due to changes in proteoglycan concentration.
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