PCR is known for its power of amplifying a target DNA sequence at a high speed. Each cycle can double the number of DNA molecules (target sequence). Which of the following is CORRECT regarding PCR?

• A. In order to make 10 copies of the DNA, you need at least 5 cycles of PCR.
• B. Helicase is required in order to separate the two strands in PCR.
• C. Dideoxynucleotides are used in PCR.
• D. DNA primers are needed in PCR.
• E. All of the above.

Answer: (D)

Verified step by step guidance

1. Understand the basic principle of PCR: PCR (Polymerase Chain Reaction) is a technique used to amplify a specific DNA segment. It involves repeated cycles of denaturation, annealing, and extension.
2. Evaluate the statement about the number of cycles needed: Each cycle of PCR doubles the amount of DNA. To make 10 copies starting from 1, calculate the number of cycles needed using the formula 2^n = number of copies, where n is the number of cycles.
3. Consider the role of helicase: In PCR, the separation of DNA strands is achieved by heating the sample to denature the DNA, not by helicase, which is used in cellular DNA replication.
4. Assess the use of dideoxynucleotides: Dideoxynucleotides are used in DNA sequencing methods like Sanger sequencing, not in PCR. PCR uses deoxynucleotides (dNTPs) for DNA synthesis.
5. Identify the correct requirement for PCR: DNA primers are essential in PCR to provide a starting point for DNA synthesis by the DNA polymerase enzyme. They anneal to the target sequence and guide the polymerase.