Biochemistry Questions and Answers Part-20

1. Which of the following does not act as a restriction enzyme?
a) EcorI
b) BamHI
c) HindIII
d) polydeoxyribonucleotide synthase

Answer: d
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

Answer: a
Explanation: Reverse transcriptase generates complementary DNA from RNA template.

3. 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

Answer: a
Explanation: (Restriction endonuclease + methylase) is termed as a restriction modification system.

4. 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

Answer: c
Explanation: The combined action of bacteriophage lambda exonuclease and terminal transferase
lead to the generation of sticky ends in plasmid vector.

5. Generally a plasmid vector contains how many elements?
a) 1
b) 2
c) 3
d) 4

Answer: c
Explanation: Cloning site, drug resistant gene and replication origin are the 3 elements in a plasmid vector.

6. To make the recombinant plasmid permeable to DNA molecules, which of the chemicals is added?
a) MgCl2
b) CaCl2
c) NaCl
d) HCl

Answer: b
Explanation: The cells are treated with CaCl2 to make them permeable to DNA molecules through a process called transformation.

7. 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

Answer: a
Explanation: Recombinant plasmid contains a drug resistant gene.

8. The extra chromosomal, self-replicating, closed, double stranded and circular DNA molecule is generally termed as __________
a) Chromosome
b) Plasmid
c) Genomic DNA
d) Bacteriophage

Answer: b
Explanation: Plasmid is an extra chromosomal, self-replicating, closed, double stranded and circular DNA molecule.

9. In which stage of genetic engineering a probe is used?
a) Cleaving DNA
b) Recombining DNA
c) Cloning
d) Screening

Answer: d
Explanation: In hybridization, which is one of the methods of screening, a probe is used.

10. 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

Answer: d
Explanation: DNA library is a collection of DNA fragments representing the entire DNA of an organism.