Class 12 Biology MCQ – The Machinery and the Enzymes for Replication of DNA

This set of Class 12 Biology Chapter 6 Multiple Choice Questions & Answers (MCQs) focuses on “The Machinery and the Enzymes for Replication of DNA”.

1. Which enzyme is used for the process of replication in E. Coli?
a) Restriction enzyme
b) Protease enzyme
c) Lipase enzyme
d) DNA polymerase
View Answer

Answer: d
Explanation: In most of the living cells of organisms like E. Coli, for the process of replication to occur, certain enzymes are used. The main enzyme which is used is a DNA dependent enzyme which is the DNA polymerase.

2. How long does it take for E. Coli to replicate?
a) 10 minutes
b) 20 minutes
c) 18 minutes
d) 21 minutes
View Answer

Answer: c
Explanation: The E. Coli has a total of 4.6 × 106 base pair. It completes its process of replication within 18 minutes. This means that the average rate of polymerisation of E. Coli DNA is 2000 base pairs per second.

3. What will happen if any abnormal changes or mistakes occur during the process of replication?
a) Mutation
b) Normal cell growth
c) Unpredictable cell deaths
d) Rapid formation of new cells
View Answer

Answer: a
Explanation: If any abnormal changes have to occur during the process of replication, mutations in the cells will arise. These changes occur if the DNA polymerase is not fast enough and also if the catalysis process is not done with high rate of accuracy.

4. In which type of process, can replication be seen at the small opening of the DNA?
a) Transformation
b) Incision
c) Mutation
d) Replication fork
View Answer

Answer: d
Explanation: In the case of large sized DNA molecules, the double strands of these molecules cannot be entirely separated. This is because, an extremely high amount of energy supply is required. So, in such cases, the process of replication fork takes place. It is a process in which a small opening is made in the portion of the DNA helix for replication to occur.

5. In which direction do the DNA dependent DNA polymerases catalyse the polymerization reaction?
a) 3’ → 5’
b) 5’ → 3’
c) In both the directions
d) Is not direction dependent
View Answer

Answer: b
Explanation: The direction for DNA dependent DNA polymerases to catalyse the polymerisation reaction is the 5’ → 3’ direction. But, in this direction of polarity, a discontinuity can be observed. These discontinuous strands of DNA can then be linked together with the help of DNA ligases. But, in the direction of 3’ → 5’ in the DNA, the replication process can be seen to be continuous.
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6. The DNA polymerase enzymes can initiate the process of replication on their own.
a) True
b) False
View Answer

Answer: b
Explanation: The DNA polymerase enzymes cannot initiate the process of replication on their own. The process of replication will also not randomly occur on any strand of the DNA, specific regions will be present. These regions are called as the origin of replication.

7. In which phase of the cell cycle does the process of replication take place in E.coli?
a) The M phase
b) The G1 phase
c) The G2 phase
d) The S phase
View Answer

Answer: d
Explanation: The process of replication will take place during the S phase of the E. Coli bacterium’s cell cycle. During this time, the replication of the DNA and the cell cycle should be highly coordinated.

8. What does the failure of cell division after DNA replication result in?
a) Polyploidy
b) Aneuploidy
c) Apoptosis
d) Migration of cells
View Answer

Answer: a
Explanation: The failure of the cell cycle process results inpolyploidy. Polyploidy is a chromosomal abnormality in which two paired sets of chromosomes are present in the cells.

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