What is a positive control in a PCR experiment?

What is a positive control in a PCR experiment?

• A. A reaction with no template DNA.
• B. A reaction designed to test non-specific primer binding.
• C. A reaction with a known template that should yield amplification.
• D. A reaction without reagents.

Answer: (C)

A positive control in PCR is a reaction that contains a known template that should yield amplification if everything is functioning properly. It confirms that the PCR reagents, enzymes, primers, and cycling conditions are working, so any lack of amplification in test samples isn’t due to a faulty setup. If the positive control amplifies as expected, you can trust the test results; if it doesn’t, you troubleshoot the assay. The other scenarios serve different purposes: a reaction with no template DNA is a negative control, used to check for contamination and should not produce a product; a reaction designed to test non-specific primer binding is about primer specificity rather than confirming the entire PCR run; a reaction without reagents is a nonfunctional setup that cannot test amplification.

A positive control in PCR is a reaction that contains a known template that should yield amplification if everything is functioning properly. It confirms that the PCR reagents, enzymes, primers, and cycling conditions are working, so any lack of amplification in test samples isn’t due to a faulty setup. If the positive control amplifies as expected, you can trust the test results; if it doesn’t, you troubleshoot the assay.

The other scenarios serve different purposes: a reaction with no template DNA is a negative control, used to check for contamination and should not produce a product; a reaction designed to test non-specific primer binding is about primer specificity rather than confirming the entire PCR run; a reaction without reagents is a nonfunctional setup that cannot test amplification.