Question

in which of the following diagrams of dna replication are the enzymes correctly labeled? choose 1 answer: a. diagram with helicase, topoisomerase, dna polymerase, ligase labels b. diagram with helicase, topoisomerase, ligase, dna polymerase labels c. diagram with topoisomerase, helicase, dna polymerase, ligase labels d. diagram with topoisomerase, helicase, ligase, dna polymerase labels

Explanation:

To determine the correct diagram, we analyze the roles of each enzyme in DNA replication:

• Topoisomerase: Relieves supercoiling ahead of the replication fork (near the original DNA helix).
• Helicase: Unwinds the DNA double helix at the replication fork (between the original helix and the replication bubble).
• DNA Polymerase: Synthesizes new DNA strands (on the leading and lagging strands).
• Ligase: Joins Okazaki fragments on the lagging strand.

• Option A: Topoisomerase and Helicase are mislabeled (Topoisomerase should be near the original helix, Helicase at the fork). Eliminate A.
• Option B: Ligase and DNA Polymerase are mislabeled (Ligase joins fragments, not synthesize; DNA Polymerase synthesizes, not join). Eliminate B.
• Option C: Enzymes are labeled correctly: Topoisomerase (relieves supercoiling), Helicase (unwinds), DNA Polymerase (synthesizes), Ligase (joins fragments).
• Option D: Ligase and DNA Polymerase are mislabeled (same error as B). Eliminate D.

Answer:

C. Topoisomerase (near original DNA), Helicase (at replication fork), DNA polymerase (synthesizing strands), Ligase (joining Okazaki fragments)