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Multiple Choice
Which of the following enzyme-function matches is incorrect?
A
Helicase - relieves tension of supercoiling by breaking and rejoining ahead of fork
B
Primase - provides short stretch of RNA at initiation of strand synthesis
C
Polymerase – synthesizes new strand of DNA while using old strand of DNA as a template.
D
DNA ligase - joins 3'-OH to 5'-phosphate to seal adjacent DNA nucleotides.
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Verified step by step guidance
1
Step 1: Begin by understanding the role of each enzyme mentioned in the problem. Helicase, Primase, Polymerase, and DNA Ligase are all involved in DNA replication, but each has a distinct function.
Step 2: Review the function of Helicase. Helicase is responsible for unwinding the DNA double helix by breaking hydrogen bonds between the complementary bases, creating a replication fork. It does not relieve supercoiling tension; that function is performed by topoisomerase.
Step 3: Examine the function of Primase. Primase synthesizes a short RNA primer that provides a starting point for DNA Polymerase to begin DNA synthesis. This description matches its correct function.
Step 4: Analyze the function of DNA Polymerase. DNA Polymerase synthesizes a new strand of DNA by adding nucleotides complementary to the template strand. This description is accurate.
Step 5: Verify the function of DNA Ligase. DNA Ligase seals nicks in the DNA backbone by joining the 3'-OH group of one nucleotide to the 5'-phosphate group of another, ensuring continuity of the DNA strand. This description is correct.