PCR-based genetic tests detect what?

• A. The entire genome sequence
• B. The expression level of a single gene
• C. The presence or absence of specific sequences
• D. The location of chromosomes in the nucleus

Answer: (C)

PCR-based genetic tests are designed to detect the presence or absence of specific DNA sequences. They use short DNA primers that match the sequence of interest; if that exact sequence exists in the sample, that region is amplified and you can detect the product, signaling a positive result. If the sequence isn’t present (or is too different for the primers to bind), no product is formed, signaling a negative result. This targeted approach makes PCR highly specific for known sequences, such as a pathogen’s DNA, a disease-associated mutation, or a diagnostic marker. It doesn’t sequence the entire genome, and on its own it doesn’t measure how much a gene is being expressed—that would require RNA-based methods like RT-PCR. It also doesn’t reveal where chromosomes are located in the nucleus; that kind of information comes from other techniques.