This set of Biochemistry Multiple Choice Questions & Answers (MCQs) focuses on “DNA Cloning: The Basics-1”.
1. Which of the following does not act as a restriction enzyme?
d) polydeoxyribonucleotide synthase
Explanation: Polydeoxtribonucleotide synthase is a DNA ligase.
2. Which of the following enzyme is responsible for making a DNA copy from RNA?
a) Reverse transcriptase
b) DNA polymerase
c) RNA polI
d) RNA polII
Explanation: Reverse transcriptase generates complementary DNA from RNA template.
3. Which of the following statements is true?
a) Exonuclease III removes nucleotide residues from the 3’ ends of a DNA strand
b) Bacteriophage lambda exonuclease removes terminal phosphates
c) Alkaline phosphatase removes nucleotides from 5‘ends
d) Kinase adds homopolymer tails to the 3’ –OH ends of a linear duplex
Explanation: Bacteriophage lambda exonuclease removes nucleotides from 5‘ends.
Alkaline phosphatase removes terminal phosphates
Terminal transferase adds homopolymer tails to the 3’ –OH ends of a linear duplex.
4. Which of the following can be termed as a restriction modification system?
a) Restriction endonuclease + methylase
b) DNA ligase + methylase
c) Restriction endonuclease + acetylase
d) DNA ligase + acetylase
Explanation: (Restriction endonuclease + methylase) is termed as a restriction modification system.
5. Which of the following is true about restriction endonucleases?
a) Type I and II requires ATP to move along DNA
b) Type I, II and III requires ATP to move along DNA
c) Type II requires no ATP and cleaves DNA within recognition sequence
d) Type II requires ATP and cleaves DNA within recognition sequence
Explanation: Type I and III requires ATP to move along DNA.
6. Which of the following enzymes’ combined action leads to the generation of sticky ends in the plasmid vector?
a) Alkaline phosphatase and terminal transferase
b) Exonuclease III and alkaline phosphatase
c) Bacteriophage lambda exonuclease and terminal transferase
d) Exonuclease III and terminal transferase
Explanation: The combined action of bacteriophage lambda exonuclease and terminal transferase
lead to the generation of sticky ends in plasmid vector.
7. Generally a plasmid vector contains how many elements?
Explanation: Cloning site, drug resistant gene and replication origin are the 3 elements in a plasmid vector.
8. To make the recombinant plasmid permeable to DNA molecules, which of the chemicals is added?
Explanation: The cells are treated with CaCl2 to make them permeable to DNA molecules through a process called transformation.
9. Which of the following statements is false?
a) The cells which take up recombinant plasmids are drug resistant
b) The cells with no recombinant plasmids are drug resistant
c) Plasmid replication is independent of cell’s division
d) The cells containing recombinant plasmid are called transformed cells
Explanation: Recombinant plasmid contains a drug resistant gene.
10. The extra chromosomal, self-replicating, closed, double stranded and circular DNA molecule is generally termed as __________
c) Genomic DNA
Explanation: Plasmid is an extra chromosomal, self-replicating, closed, double stranded and circular DNA molecule.
11. E.cor1 is a __________
a) DNA ligase enzyme
b) Restriction endonuclease
c) A vector used for insulin synthesis
d) A plasmid used as a vector
Explanation: Ecor1 is a restriction enzyme that cleaves vector at the cloning site.
12. In which stage of genetic engineering a probe is used?
a) Cleaving DNA
b) Recombining DNA
Explanation: In hybridization, which is one of the methods of screening, a probe is used.
13. What is a DNA library?
a) A DNA fragment inserted into a vector
b) A general collection of all genes sequenced thus far
c) All DNA fragments identified with a probe
d) A collection of DNA fragments that make up the entire genome of a particular organism
Explanation: DNA library is a collection of DNA fragments representing the entire DNA of an organism.
14. Which of the following enzyme is required for end to end joining of DNA?
a) DNA ligase
b) Restriction endonuclease
c) RNA polymerase
d) DNA polymerase
Explanation: DNA ligase ligates both blunt and sticky ends of DNA.
15. Repressor molecules bind to __________
d) Hormone response element
Explanation: An operator lies partially within the promoter, repressor binds to the DNA at operator region inhibiting the expression of genes.
Sanfoundry Global Education & Learning Series – Biochemistry.
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