THE MOLECULAR BASIS OF INHERITANCE
DNA REPLICATION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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relieve stress in DNA in front of the replication fork
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unwind the double helix by breaking hydrogen bonds
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add nucleotides to the new strand of DNA
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add an RNA primer to the new strand of DNA
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Detailed explanation-1: -Topoisomerase action ahead of the fork, by either type I or type II topoisomerases, relaxes the positive helical stress in the parental strands, preventing topological stress from arresting the progression of DNA replication (Figure 1A).
Detailed explanation-2: -But there is a built-in tension reliever in the form of another enzyme called topoisomerases. These enzymes can reduce the stress by either cutting one or both strands, throwing one strand around the other and resealing it back.
Detailed explanation-3: -Topoisomerases play critical roles in DNA replication, transcription, and chromosome structure by altering the topological state of DNA, . These enzymes are capable of relaxing supercoiled DNA and of decatenating interlocked DNA (Fig.
Detailed explanation-4: -DNA gyrase, is the type II topoisomerase enzyme that is primarily involved in relieving positive supercoiling tension that results due to the helicase unwinding at the replication fork.
Detailed explanation-5: -The untwisting of the double helix by helicase causes additional twisting of the DNA molecule ahead of the replication fork. Topoisomerase is the enzyme that helps to relieve this strain by breaking, untwisting and rejoining the DNA strands.