Name the main enzymes involved in bacterial DNA replication and briefly state their roles.

Name the main enzymes involved in bacterial DNA replication and briefly state their roles.

• A. Helicase unwinds the double helix; primase lays down RNA primers; DNA polymerase III extends new strands; DNA polymerase I replaces primers with DNA; DNA ligase seals nicks; topoisomerase relieves supercoiling.
• B. Helicase seals nicks; primase copies RNA primers; DNA polymerase II extends; DNA ligase repairs; topoisomerase inhibits replication.
• C. Nuclease cuts DNA; ligase removes primers; polymerase I winds the helix; helicase seals nicks; gyrase degrades supercoils.
• D. Topoisomerase unwinds; primase blocks primers; DNA polymerase IV fills gaps; ligase opens nicks; helicase substitutes primers.

Answer: (A)

Enzymes coordinating replication fork progression. Helicase unwinds the double helix to create the replication fork, using energy from ATP. Primase lays down short RNA primers to provide starting points with free 3' ends for DNA synthesis. DNA polymerase III is the main enzyme that adds nucleotides to build the new DNA strands, highly processive with the help of the sliding clamp. On the lagging strand, DNA polymerase I removes the RNA primers and fills the gaps with DNA. DNA ligase then seals the remaining nicks between Okazaki fragments to create a continuous strand. Topoisomerase relieves the torsional stress and supercoiling that build up ahead of the fork, preventing tangling of the DNA. Other descriptions mix up these roles or name enzymes not primarily responsible for replication in bacteria (for example, misassigning primer handling, using non-replicative polymerases, or saying topoisomerase inhibits replication).

Enzymes coordinating replication fork progression. Helicase unwinds the double helix to create the replication fork, using energy from ATP. Primase lays down short RNA primers to provide starting points with free 3' ends for DNA synthesis. DNA polymerase III is the main enzyme that adds nucleotides to build the new DNA strands, highly processive with the help of the sliding clamp. On the lagging strand, DNA polymerase I removes the RNA primers and fills the gaps with DNA. DNA ligase then seals the remaining nicks between Okazaki fragments to create a continuous strand. Topoisomerase relieves the torsional stress and supercoiling that build up ahead of the fork, preventing tangling of the DNA.

Other descriptions mix up these roles or name enzymes not primarily responsible for replication in bacteria (for example, misassigning primer handling, using non-replicative polymerases, or saying topoisomerase inhibits replication).