Which of the following is NOT a standard component of a PCR (Polymerase Chain Reaction) mixture? Select the best answer.

• A. DNA primers
• B. DNA template
• C. DNA ligase
• D. Taq DNA polymerase

Answer: (C)

Verified step by step guidance

1. Understand the purpose of PCR (Polymerase Chain Reaction): PCR is a technique used to amplify specific DNA sequences. It requires certain components to function effectively.
2. Review the standard components of a PCR mixture: These typically include DNA primers (short sequences that bind to the target DNA), a DNA template (the sequence to be amplified), Taq DNA polymerase (an enzyme that synthesizes new DNA strands), and nucleotides (dNTPs) to build the new DNA strands.
3. Analyze the role of DNA ligase: DNA ligase is an enzyme that joins DNA fragments together by forming phosphodiester bonds. It is commonly used in DNA replication and repair but is not required for PCR, as PCR does not involve joining DNA fragments.
4. Compare DNA ligase to Taq DNA polymerase: Taq DNA polymerase is specifically designed to withstand the high temperatures of PCR and synthesize DNA strands, whereas DNA ligase has no role in amplifying DNA during PCR.
5. Conclude that DNA ligase is NOT a standard component of a PCR mixture, as it does not contribute to the amplification process.