Question

DNA topoisomerases: Which of the following functions as reversible nucleuses that permit DNA unwinding without the need for chromosomal rotation?

1) Attach long sequences to the ends of eukaryotic chromosomes
2) Allow DNA to properly rewind after replication
3) Function as replication proof readers to identify errors
4) Reversible nucleuses that permit DNA unwinding without the need for chromosomal rotation
5) Make single cuts in DNA to remove mismatched single strands

Answer 1

The correct function of DNA topoisomerases is to act as reversible nucleases that permit DNA unwinding without the need for the entire chromosome to rotate, which is option 4. The correct answer is option 4.

Step-by-step explanation:

DNA topoisomerases are critical enzymes that play a role in managing the topology of DNA during replication. These enzymes are remarkable for their ability to perform the function of a reversible nuclease, which helps in unwinding the DNA without requiring the entire chromosome to rotate. This function is essential to prevent the supercoiling that would otherwise occur due to the unwinding of the double helix as replication progresses. Topoisomerases act by making either single or double-stranded cuts in the DNA to release the tension caused by supercoiling, after which they reconnect the broken strands.

The correct answer to the presented question is 4) Reversible nucleases that permit DNA unwinding without the need for chromosomal rotation. This allows DNA replication to proceed efficiently by solving the problem that would occur from the tension generated by the winding and unwinding of DNA. The topoisomerase enzyme wraps around the DNA and makes a critical cut, allowing the DNA helix to relax and spin. After the tension has been relieved, the topoisomerase then reseals the broken DNA strands.

During the process of DNA replication, other key enzymes and proteins such as helicase, single-strand binding proteins, primase, DNA polymerase, and DNA ligase also play vital roles in unwinding the DNA, preventing the strands from rewinding, synthesizing RNA primers, adding nucleotides to the growing strand, and sealing the gaps between synthesized DNA fragments, respectively.

Overall, topoisomerases ensure that the supercoiling pressure does not become detrimental to the cell by causing breaks in the phosphodiester bonds of the DNA leading to fragmentation. They facilitate a smooth replication process, which is crucial for cell division and the maintenance of genetic information.