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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helicase
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primase
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gyrase/topoisomerase
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ligase
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Detailed explanation-1: -DNA is normally supercoiled. Supercoiled DNA is under too much tension to be separated, so an extra step is required before replication and transcription can occur. DNA gyrase relaxes supercoiled DNA by cutting it, allowing rotation to occur, and then reattaching it.
Detailed explanation-2: -Topoisomerase V relaxes supercoiled DNA by a constrained swiveling mechanism.
Detailed explanation-3: -DNA supercoiling plays an important role in replication, repair, recombination, transposition and transcription. DNA topoisomerases type I are ATP-independent enzymes that cut one DNA strand and relax supercoiled molecules. DNA topoisomerases type II requiere ATP, cut both DNA strands and supercoil relaxed molecules.
Detailed explanation-4: - DNA topoisomerases are ubiquitous enzymes found in all cell types from viruses to man. These enzymes act to regulate DNA supercoiling by catalysing the winding and unwinding of DNA strands.
Detailed explanation-5: -Topoisomerases are enzymes that release the tension in DNA strands. When a DNA strand undergoes replication or transcription, the strand that is ahead of the replication fork starts to owerwind.