In the gene probe procedure, what is the purpose of heating the DNA sample?

• A. To allow the probe to hybridize to complementary single-stranded DNA
• B. To activate the radioactive label
• C. To degrade non-target DNA
• D. To denature the probe

Answer: (A)

Heating the DNA sample denatures the double-stranded DNA, turning it into single strands. This exposes the target sequences so the labeled probe, which is complementary in sequence, can find and bind to its matching region through base pairing. After the heat step, cooling allows the probe to anneal specifically to its target; non-specific bindings are less stable at the annealing temperature, helping ensure a true hybrid. Heating does not activate the label or degrade non-target DNA, and the probe is typically already single-stranded, so the main purpose is to make the target accessible for specific hybridization.