Class 12 Biology · Chapter 7 · Test 2
DNA Replication
39 MCQs
39 questions · 35 min · 39 marks
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Sample questions
The first 5 of 39. Try each one, then tap to see the answer.
Question 1
Which of the following is NOT involved in the initiation of replication?
- ADNA ligase
- BDNA gyrase
- CSingle-stranded binding protein
- DPrimase
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Answer: A
DNA ligase joins Okazaki fragments at termination and is not needed to start replication.
Question 2
Why does DNA polymerase synthesise the leading and lagging strands of DNA in different manners?
- AThe origins of replication occur only at the 5' end
- BDNA ligase works only in the 3' to 5' direction
- CDNA polymerase can only work on one strand at a time
- DDNA polymerase can join new nucleotides only to the 3' end of strand
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Answer: D
Because the strands run in opposite directions one is built continuously and the other discontinuously.
Question 3
Synthesis of a new DNA strand usually begins with:
- ARNA primer
- BDNA primer
- CDNA ligase
- DOkazaki fragment
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Answer: A
Primase makes a short RNA primer from which DNA polymerase starts.
Question 4
The elongation of the leading strand during DNA synthesis:
- AProgresses away from the replication fork
- BOccurs in the 3' to 5' direction
- CProduces Okazaki fragments
- DDepends on the action of polymerase
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Answer: D
The leading strand is built continuously by DNA polymerase in the direction of fork movement.
Question 5
Which of the following enzymes removes supercoiling in replicating DNA ahead of the replication fork?
- ADNA polymerases
- BHelicases
- CPrimases
- DTopoisomerases
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Answer: D
Gyrase or topoisomerase prevents supercoiling ahead of the fork.
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