Which component is required to initiate DNA synthesis in PCR?

Which component is required to initiate DNA synthesis in PCR?

• A. DNA polymerase (e.g., Taq polymerase) along with primers, nucleotides, and buffer.
• B. RNA polymerase and transcription factors.
• C. DNA ligase and primers only.
• D. Helicase alone.

Answer: (A)

DNA synthesis in PCR begins when a DNA polymerase enzyme extends from a primer, using nucleotides as building blocks and working under the right buffer conditions. The primers provide starting points with a 3' end for the polymerase to add nucleotides, so synthesis can begin and be copied across cycles. The polymerase alone wouldn’t start anything without these primers and substrates, and the buffer ensures the enzyme functions optimally at the temperatures used in PCR. The other options don’t fit because RNA polymerase would make RNA, not DNA; DNA ligase only joins existing DNA strands and doesn’t initiate synthesis; helicase only unwinds DNA, not synthesize new strands. So the combination of DNA polymerase with primers, nucleotides, and buffer is required to initiate DNA synthesis in PCR.

DNA synthesis in PCR begins when a DNA polymerase enzyme extends from a primer, using nucleotides as building blocks and working under the right buffer conditions. The primers provide starting points with a 3' end for the polymerase to add nucleotides, so synthesis can begin and be copied across cycles. The polymerase alone wouldn’t start anything without these primers and substrates, and the buffer ensures the enzyme functions optimally at the temperatures used in PCR.

The other options don’t fit because RNA polymerase would make RNA, not DNA; DNA ligase only joins existing DNA strands and doesn’t initiate synthesis; helicase only unwinds DNA, not synthesize new strands. So the combination of DNA polymerase with primers, nucleotides, and buffer is required to initiate DNA synthesis in PCR.