Which technique uses a gene probe to detect a specific DNA sequence?

• A. PCR amplification
• B. Hybridization assay
• C. Western blot
• D. Mass spectrometry

Answer: (B)

Detecting a specific DNA sequence with a gene probe relies on complementary base pairing between a labeled probe and the target DNA. In a hybridization assay, a nucleic acid probe designed to be complementary to the sequence of interest is labeled and allowed to bind to the DNA sample. If the target sequence is present, the probe anneals to it, and the attached label (radioactive, fluorescent, or enzymatic) produces a detectable signal, confirming presence and often enabling localization or sizing. This approach hinges on the specificity of base pairing, which is why it’s used to identify particular DNA sequences. The other methods work differently: PCR amplifies DNA with primers rather than using a binding probe for detection; Western blot analyzes proteins with antibodies; mass spectrometry identifies molecules by mass, not by sequence-specific hybridization.