This set of Biochemistry Multiple Choice Questions & Answers (MCQs) focuses on “DNA Replication”.
1. What is DNA replication?
a) Conservative
b) Non-conservative
c) Semi-conservative
d) None of the mentioned
View Answer
Explanation: Each DNA strand serves as a template for the synthesis of a new strand, producing two new DNA molecules, each with one new strand and one old strand.
2. Semi-conservative DNA replication was first demonstrated in ____________
a) Drosophila melanogaster
b) Escherichia coli
c) Streptococcus pneumonae
d) Drosophila melanogaster
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Explanation: Semi-conservative DNA replication was first demonstrated in E. coli.
3. Eukaryotes differ from prokaryote in mechanism of DNA replication due to ____________
a) Use of DNA primer rather than RNA primer
b) Different enzyme for synthesis of lagging and leading strand
c) Discontinuous rather than semi-discontinuous replication
d) Unidirectional rather than semi-discontinuous replication
View Answer
Explanation: In eukaryotes one strand of DNA is synthesized continuously but the other one is made of Okazaki fragments.
4. Which of the following is true about DNA polymerase?
a) It can synthesize DNA in the 5’ to 3’ direction
b) It can synthesize DNA in the 3’ to 5’ direction
c) It can synthesize mRNA in the 3’ to 5’ direction
d) It can synthesize mRNA in the 5’ to 3’ direction
View Answer
Explanation: DNA pol can synthesize only a new DNA strand not m-RNA. It can do this in the 5’ to 3’ direction.
5. What is the reaction in DNA replication catalyzed by DNA ligase?
a) Addition of new nucleotides to the leading strand
b) Addition of new nucleotide to the lagging strand
c) Formation of a phosphodiester bond between the 3’-OH of one Okazaki fragment and the 5’-phosphate of the next on the lagging strand
d) Base pairing of the template and the newly formed DNA strand
View Answer
Explanation: DNA ligase catalyzes the formation of a phosphodiester bond between 3’-OH of one Okazaki fragment and 5’-phosphate of the next.
6. Which of the following reactions is required for proofreading during DNA replication by DNA polymerase III?
a) 5’ to 3’ exonuclease activity
b) 3’ to 5’ exonuclease activity
c) 3’ to 5’ endonuclease activity
d) 5’ to 3’ endonuclease activity
View Answer
Explanation: The 3’ → 5’ exonuclease activity removes the mispaired nucleotide and the polymerase begins again. This activity is known as proofreading.
7. Which of the following enzymes remove supercoiling in replicating DNA ahead of the replication fork?
a) DNA polymerases
b) Helicases
c) Primases
d) Topoisomerases
View Answer
Explanation: Strand separation creates topological stress in the helical DNA structure which is relieved by the action of topoisomerases.
8. DNA unwinding is done by ____________
a) Ligase
b) Helicase
c) Topoisomerase
d) Hexonuclease
View Answer
Explanation: These enzymes move along the DNA and separate the strands using chemical energy from ATP.
9. Which of the following enzymes is the principal replication enzyme in E. coli?
a) DNA polymerase I
b) DNA polymerase II
c) DNA polymerase III
d) None of the mentioned
View Answer
Explanation: Only DNA pol III is the principal replication enzyme in E. coli.
10. Which enzyme used to join bits of DNA?
a) DNA polymerase
b) DNA ligase
c) Endonuclease
d) Primase
View Answer
Explanation: DNA ligase can be used to join the nicked sites.
Sanfoundry Global Education & Learning Series – Biochemistry.
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