Probe

**Semantic type:** Chemical Viewed Functionally

**Definition:** General term for a piece of DNA or RNA corresponding to a gene or sequence of interest, that has been labelled either radioactively or with some other detectable molecule, such as biotin, digoxygenin or fluorescein. As stretches of DNA or RNA with complementary sequences will hybridize, a probe will label viral plaques, bacterial colonies or bands on a gel that contain the gene of interest.