What is a negative control in a PCR experiment?

What is a negative control in a PCR experiment?

• A. A reaction with a known template that yields amplification.
• B. A reaction with no template DNA (no-template control) to detect contamination or non-specific amplification.
• C. A reaction designed to test robustness of cycling conditions.
• D. A reaction with contaminated reagents.

Answer: (B)

A negative control in PCR is a reaction that should yield no amplification because it contains everything except the DNA template. Typically this is a no-template control, where water or buffer replaces the DNA. Its purpose is to reveal contamination or carryover of amplified products, and to detect any non-specific amplification arising from the reagents themselves. If this control shows amplification, it signals that results from the actual samples could be false positives due to contamination or unexpected activity in the setup. In contrast, a positive control includes a known template to confirm the reaction can amplify, a test of robustness would focus on how cycling conditions perform, and a reaction with contaminated reagents is not a valid control and would indicate a problem rather than validate the assay.

A negative control in PCR is a reaction that should yield no amplification because it contains everything except the DNA template. Typically this is a no-template control, where water or buffer replaces the DNA. Its purpose is to reveal contamination or carryover of amplified products, and to detect any non-specific amplification arising from the reagents themselves. If this control shows amplification, it signals that results from the actual samples could be false positives due to contamination or unexpected activity in the setup. In contrast, a positive control includes a known template to confirm the reaction can amplify, a test of robustness would focus on how cycling conditions perform, and a reaction with contaminated reagents is not a valid control and would indicate a problem rather than validate the assay.