Molecular Biology Multiple Choice Questions on “Properties of DNA Polymerase – 1”.
1. Which of the following types of DNA polymerase has 3’→5’ exonuclease activity?
A. DNA polymerase I
B. DNA polymerase II
C. DNA polymerase III
D. DNA polymerase IV
Answer: A
Explanation: DNA polymerases I, II, III and IV all has 5’→3’ exonuclease activity. DNA polymerases I is the only polymerase to have the 3’→5’ exonuclease activity which is the proof reading activity of DNA polymerase.
2. Choose the odd one out with respect to DNA polymerase III.
A. dna E
B. dna N
C. dna Q
D. dna B
Answer: D
Explanation: DNA polymerase III is the product of dna E, dna N, dna Q and 7 other structural genes. Only dna B is the odd one in the provided group as it is not the structural gene for any of the subunits of DNA polymerase III.
3. Which of the following is used in prokaryotic replication?
A. DNA polymerase I
B. DNA polymerase II
C. DNA polymerase III
D. DNA polymerase δ
Answer: C
Explanation: Prokaryotic replication is polymerized by the enzyme DNA polymerase III. DNA polymerase I, DNA polymerase II and DNA polymerase δ all take part in the eukaryotic replication.
4. DNA polymerase II can polymerase upto ______________ nucleotides per minute at 37˚C.
A. 50
B. 500
C. 5000
D. 50000
Answer: A
Explanation: DNA polymerase II has the lowest affinity for dNTPs and can polymerase upto 50 nucleotides per minute at 37˚C. DNA polymerase III has the highest affinity for dNTPs and can polymerase upto 15000 nucleotides per minute at 37˚C.
5. All mutation in polymerases is lethal except the mutation of polymerase III.
A. True
B. False
Answer: B
Explanation: Mutations in both DNA polymerase I and DNA polymerase III are lethal. Only exception to this is polymerase III, mutation to which is not lethal.
6. Polymerase I has the highest affinity for dNTPs.
A. True
B. False
Answer: B
Explanation: DNA polymerase I have a low affinity for dNTPs and can polymerase upto 1000 nucleotides per minute at 37˚C. DNA polymerase III has the highest affinity for dNTPs and can polymerase upto 15000 nucleotides per minute at 37˚C.
7. Polymerase I has two fragments. The residue of larger fragment consists from ____________ residues.
A. 1 – 234
B. 234 – 658
C. 324 – 928
D. 234 – 928
Answer: C
Explanation: Polymerase I has two fragments. The residue of larger fragment consists from 324 – 928 residues is known as the Klenow fragment which has the polymerase activity as well as the 5’→3’ exonuclease activity.
8. Which of the following is false about klenow fragment?
A. Polymerization activity
B. 3’→5’ exonuclease activity
C. 5’→3’ exonuclease activity
D. 324 – 928 residue of polymerase I
Answer: B
Explanation: The residue of larger fragment consists from 324 – 928 residues is known as the klenow fragment which has the polymerase activity as well as the 5’→3’ exonuclease activity. The 3’→5’ exonuclease activity or the proofreading activity is present in the small fragment of DNA polymerase I.
9. DNA polymerase III has ___________ subunits.
A. 4
B. 6
C. 8
D. 10
Answer: D
Explanation: DNA polymerase II has 10 subunits. They are αa, ϵa, θa, τ, γb, δb, δ’b, χb, Ψb and β the structural genes of which are pol C, dna Q, hot E, dna xc, dna χc, hot A, hot B, hot C, hot D and dna N respectively.
10. Which of the following types of DNA polymerase does not take part in DNA repair?
A. DNA polymerase I
B. DNA polymerase II
C. DNA polymerase III
D. DNA polymerase IV
Answer: C