Final answer:
DNA replication requires topoisomerases, deoxyribonucleoside triphosphates, and an RNA primer synthesized from ribonucleoside triphosphates. Based on the options, the answer could be (4) An and B only but considering all required components including RNA primers, the answer is (5) All of the above.
Step-by-step explanation:
DNA replication requires a series of enzymes and precursors to successfully synthesize a new DNA strand. The components necessary for this intricate process include: topoisomerases, which help alleviate the supercoiling of DNA that occurs as the helix unwinds; deoxyribonucleoside triphosphates (dNTPs), which are the building blocks that are added to the growing DNA strand; and an RNA primer, often synthesized by primase, which provides a starting point for DNA polymerase to begin adding dNTPs. Based on the options provided, the direct answer to the question would be (4) An and B only, meaning topoisomerases and deoxyribonucleoside triphosphates are required, but ribonucleoside triphosphates (in the context of RNA primers) are also implicitly necessary for the replication to initiate.
It is important to note that the RNA primers mentioned in the options are made of ribonucleoside triphosphates, which are indeed necessary for the primase to synthesize the RNA primer that DNA polymerases then extend with deoxyribonucleoside triphosphates. Although not explicitly listed in the answer options, these primers are an essential part of the initiation of DNA replication. Therefore, the most technically accurate response considering all required components would be (5) All of the above.