How do radioactive DNA probes work?

So radioactive DNA probes are basically single strands of DNA or RNA with a radioactive tag. Their sequence is usually the complementary of a single sequence of DNA that researchers want to find in an array of other DNA (such as a gene).

So they tag this probe, and release it. They track it to see where it binds in the array of DNA. Once it binds, they know they've found their target DNA.

Hope that helped :)