This set of Genetic Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Cultured Cells in Mammals and Restricted Areas in Intact Organisms – 1”.
1. Lesch-Nyhan syndrome is caused by the deficiency of the enzyme hypoxanthine-guanine phosphoribosyl transferase (HGPRT). Cells deficient in HGPRT die in a medium containing which of the following?
a) Hypoxanthine and thymidine
b) Thymidine
c) Aminopterin and thymidine
d) Hypoxanthine, thymidine and aminopterin (HAT medium)
View Answer
Explanation: HGPRT deficient cells in the medium containing all three hypoxanthine, thymidine and aminopterin. It is so because aminopterin blocks the endogenous synthesis of purines needed for the synthesis of nucleic acid.
2. Presence of wild-type DNA onto the HGPRT– in the presence of _______ led to DNA uptake and stable transformation.
a) lithium acetate
b) calcium phosphate
c) sodium chloride
d) aluminum sulphate
View Answer
Explanation: Presence of wild type in HGPRT—in the presence of calcium phosphate led to DNA uptake and stable transformation.
3. Cells deficient in thymidine kinase (TK) are also killed in HAT medium.
a) True
b) False
View Answer
Explanation: Cells deficient in thymidine kinase are also killed in HAT medium. It is so because pyrimidine synthesis is also blocked in the presence of aminopterin and utilization of thymidine in the HAT medium requires a functional TK.
4. Hygromycin is used as a selectable marker in mammalian cultured cells. It is used for ____________
a) initiating protein synthesis
b) inhibiting protein synthesis
c) initiating DNA binding process
d) inhibiting DNA binding process
View Answer
Explanation: Hygromycin is used as a protein synthesis inhibitor. It is conferred by a bacterial hph gene which encodes hygromycin phosphotransferase. Resistance to hygromycin is used as a selectable marker.
5. Puromycin is a protein synthesis inhibitor. It is conferred by _______ gene.
a) streptococcal
b) bacilovirus
c) streptomyces
d) both streptococcal and streptomyces
View Answer
Explanation: Puromycin is a protein synthesis inhibitor and is conferred by streptomyces gene. It does so by encoding puromycin-N-acetyltransferase.
6. Resistance to bleomycin (zeocin) is used as a selectable marker for mammalian cultured cells and its function is ____________
a) DNA damaging agent
b) DNA synthesis promoter
c) Inhibiting RNA synthesis
d) Activating RNA synthesis
View Answer
Explanation: Resistance to bleomycin (zeocin) is used as a selectable marker for mammalian cultured cells and it is a DNA damaging agent. It does so by expression of a binding protein.
7. Resistance to methotrexate, which inhibits the enzyme dihydrofolate reductase (DHFR) is used as a selectable marker. This enzyme is involved in the synthesis of _____ carbon units and is required for _____ biosynthesis.
a) two, nucleoside
b) two, nucleotide
c) one, nucleotide
d) one, nucleoside
View Answer
Explanation: Resistance to methotrexate, which is used as a selectable marker inhibits DHFR enzyme. This enzyme is involved in the synthesis of one carbon units and is required for nucleoside synthesis.
8. Histidinol dehydrogenase allows synthesis of histidine from exogenous histanol.
a) True
b) False
View Answer
Explanation: Histidinol dehydrogenase is also used as a selectable marker. It allows synthesis of histdidine from exogenous histanol and protects from toxic effects of histidinol.
9. Many mammalian cells contain Thymidine Kinase, the mammalian enzyme uses the analogue _____ than does the viral enzyme.
a) more efficiently
b) less efficiently
c) with same efficiency
d) either with same or more efficiency
View Answer
Explanation: Many mammalian cells contain thymidine kinase, the mammalian enzyme uses the analogue less efficiently than the viral enzyme. If cells lack viral enzyme they are resistant to analogue and are able to grow in a mammalian enzyme.
10. A wide range of host cell lines are available and commonly used human cell lines are obtained from ___________
a) kidney
b) liver
c) lymphoblast from leukaemia patient
d) both kidney and lymphoblast from a leukaemia patient
View Answer
Explanation: There is a wide range of host cell lines available. Commonly used human cell lines are HeLa 293T, obtained from kidney and Jurkat which is obtained from lymphoblast from a leukaemia patient.
11. DEAE-dextran is used for introduction of DNA. It is a modified _____ and is ______
a) polysaccharide, negatively
b) polysaccharide, positively
c) monosaccharide, positively
d) monosaccharide, negatively
View Answer
Explanation: There are various methods for the uptake of transformation DNA such as electroporation and DEAE-dextran method. It is a modified polysaccharide and is positively charged. It forms a complex with negatively charged DNA and is taken into cells by endocytosis.
12. Cells whose contents have been removed and replaced, by swelling and shrinking in solutions of suitable osmotic strength are called as ____________
a) protoplast
b) ghosts
c) shrunken cells
d) vacuole
View Answer
Explanation: Ghosts are those cells whose contents have been removed and replaced by swelling and shrinking in solutions of suitable osmotic strength. Red blood ghosts are also used for the introduction of DNA into mammalian cells.
13. In ___________ cells, virus replication doesn’t take place and viral DNA ___________
a) non-permissive, is also not expressed
b) permissive, is also not expressed
c) non-permissive, can be expressed
d) non-permissive, is always expressed
View Answer
Explanation: In non-permissive cells, virus replication doesn’t take place and viral DNA can be expressed though.
14. SV40 is a virus and it produces how many transcripts?
a) 1
b) 2
c) 3
d) 4
View Answer
Explanation: SV40 is a virus and it produces two transcripts. These transcripts are produced by early and late transcripts.
15. Splicing of the transcripts is necessary for efficient expression.
a) True
b) False
View Answer
Explanation: Splicing of both the transcripts is necessary and it is for efficient expression. Sequences that have not been through the splicing process are not expressed efficiently even if introns are removed.
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