This set of Vector Biology Multiple Choice Questions & Answers (MCQs) focuses on “Vectors for Mammals – 4”.
1. How many routes are available for the biosynthesis of nucleotides in human beings?
a) 1
b) 2
c) 3
d) 4
View Answer
Explanation: In mammals, nucleotides are produced via two alternate routes, the de novo and the salvage pathway.
2. What are the basic precursors in the de novo pathway of nucleotide synthesis?
a) Carbohydrate, proteins
b) Sugars, amino acids
c) Sugars, vitamins
d) Minerals, carbohydrates
View Answer
Explanation: In mammals, nucleotides are produced via two alternate routes, the de novo and the salvage pathway. In the de novo pathway, nucleotides are synthesized from basic precursors such as sugars and amino acids.
3. In the salvage pathway, nucleotides are synthesized by the recycling of ___________
a) DNA
b) RNA
c) DNA, RNA
d) Sugars
View Answer
Explanation: In mammals, nucleotides are produced via two alternate routes, the de novo and the salvage pathway. Salvage pathway recycles nucleotides from DNA and RNA.
4. De novo pathway is exploited for the selection of cells carrying functional HPRT and TK genes.
a) True
b) False
View Answer
Explanation: If the de novo pathway is blocked, nucleotide synthesis becomes dependent on the salvage pathway, and this can be exploited for the selection of cells carrying functional HPRT and TK genes.
5. The drug aminopterin blocks the _________ of two enzymes.
a) Salvage pathway
b) De novo synthesis
c) Expression
d) Recombination
View Answer
Explanation: The drug aminopterin blocks the de novo synthesis of inosine monophosphate (IMP) and thymidine monophosphate (TMP).
6. What do you understand by the term “co-transformation”?
a) Integration of 2 transgenes
b) Integration of similar transgenes
c) Integration of a group of transgenes
d) Integration of chromosomal DNA
View Answer
Explanation: The transfection with two physically unlinked DNAs results in co-transformation that is the integration of both the transgenes into the genome.
7. Southern blot hybridization is done for testing the presence of _________ in a selection of transformants.
a) Non-selected DNA
b) Selected plasmid DNA
c) Genomic DNA
d) Selected genomic DNA
View Answer
Explanation: To obtain co-transformants, cells were transfected with HSV Tk gene and well defined plasmid DNA. Cells selected on HAT medium are then tested by southern blotting for the presence of non-selected DNA.
8. What is the prerequisite for co-transformation phenomenon to occur?
a) Selectable marker
b) HSV
c) Thymidine kinase
d) PBR322 DNA
View Answer
Explanation: The phenomenon of co-transformation allows the stable introduction of any foreign DNA sequence into mammalian cells as long as a selectable marker is introduced at the same time.
9. HSV TK gene is a type of __________ marker.
a) Exogenous
b) Endogenous
c) Recombinant
d) Hybrid
View Answer
Explanation: The HSV Tk gene is a representative of a class of genes known as endogenous markers because they confer a property that is already present in the wild-type cells.
10. The endogenous selectable markers can be used only with mutant cell lines.
a) True
b) False
View Answer
Explanation: The major disadvantage of the endogenous selectable markers is that they can only be used with mutant cell lines in which the corresponding host gene is non-functional.
11. Dominant selectable markers can be used with __________
a) Any cell type
b) Mutant cells
c) Wild-type cells
d) Recombinant cells
View Answer
Explanation: Endogenous markers are largely superseded by so-called dominant selectable markers, which confer a phenotype that is entirely novel to the cell and can hence be used in any cell type.
12. What are the dominant selectable markers?
a) Drug-resistance genes
b) Inducing genes
c) Exogenous genes
d) Endogenous genes
View Answer
Explanation: The dominant selectable markers are usually drug-resistance genes of bacterial origin and transformed cell is selected on a medium that contains the drug at an appropriate concentration.
13. Methotrexate is an analog of __________
a) Aminopterin
b) Kanamycin
c) Folic acid
d) Gentamycin
View Answer
Explanation: Methotrexate is a folic acid analog, which is a competitive inhibitor of the enzyme dihydrofolate reductase (DHFR).
14. With respect to mammalian cell cloning, salmon sperm DNA can serve as a source of ____________
a) Non-specific carrier
b) Specific carrier
c) Genomic DNA
d) Plasmid DNA
View Answer
Explanation: Calcium phosphate transfection is mostly used and the specific donor DNA is often bulked with a non-specific carrier such as cleaved Salmon sperm.
15. One application in which the use of plasmid vectors is critical, in the case of mammals is ____________
a) Stable transformation
b) Transient transformation
c) Transfection
d) Transduction
View Answer
Explanation: One application in which the use of plasmid vectors is critical, in the case of mammals is a transient transformation. Here the goal is to exploit the short term persistence of extrachromosomal DNA.
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