Match the enzyme with its role in prokaryotic DNA replication. Group of answer choices DNA polymerase I an exonuclease that removes RNA primers DNA polymerase III cuts DNA to release concatenated chromosomes and reseals the DNA Topoisomerase II relaxes supercoils and relieves stress on DNA Topoisomerase IV adds nucleotides in the 5′ to 3′ direction to produce the new complementary strand of DNA during replication
The Correct Answer and Explanation is:
Correct Matching:
- DNA polymerase I – an exonuclease that removes RNA primers
- DNA polymerase III – adds nucleotides in the 5′ to 3′ direction to produce the new complementary strand of DNA during replication
- Topoisomerase II – relaxes supercoils and relieves stress on DNA
- Topoisomerase IV – cuts DNA to release concatenated chromosomes and reseals the DNA
Explanation
DNA replication in prokaryotes is a highly coordinated process involving multiple enzymes, each with a specific and essential role. Among the primary enzymes are DNA polymerases and topoisomerases, which function to replicate and manage DNA topology during replication.
DNA polymerase III is the main enzyme responsible for synthesizing new DNA strands. It adds nucleotides in the 5′ to 3′ direction, using the original DNA strand as a template. This enzyme possesses high processivity and proofreading ability, ensuring accurate DNA synthesis.
DNA polymerase I plays a crucial role in processing Okazaki fragments formed on the lagging strand. It has both 5′ to 3′ polymerase activity and 5′ to 3′ exonuclease activity. The exonuclease activity allows it to remove RNA primers that are initially laid down by primase. After removing the RNA primers, DNA polymerase I fills in the resulting gaps with DNA nucleotides.
Topoisomerase II, also known as DNA gyrase in prokaryotes, helps to manage DNA supercoiling that occurs ahead of the replication fork. As the DNA double helix is unwound by helicase, it creates torsional strain. Topoisomerase II alleviates this strain by making temporary double-stranded breaks in the DNA, passing another portion of the double helix through the break, and then resealing the DNA. This prevents the DNA from becoming too tightly coiled and ensures smooth replication.
Topoisomerase IV is essential in the final stages of DNA replication. After the replication of circular prokaryotic chromosomes, the two daughter DNA molecules often become interlinked (concatenated). Topoisomerase IV resolves this by making double-stranded cuts in one DNA molecule, allowing the other to pass through, thus separating the interlinked chromosomes. It then reseals the break, ensuring that each daughter cell receives a complete chromosome.
Together, these enzymes ensure the fidelity, continuity, and manageability of DNA during replication in prokaryotic cells.
