SIDEBAR: Selected Suppliers of DNA and RNA Probes

In the doctor's office or the research lab, the supreme value of DNA and RNA as diagnostic tools and the high potential of genetic therapy are putting a premium on DNA and RNA probes.

Probes are short, single-stranded chains of nucleic acid that seek out and latch themselves to a complementary sequence of nucleic acids, often buried anonymously in a much larger section of DNA/RNA. Guanine on one chain links to a cytosine counterpart (G-C), and adenine closes on thymine (G-T). If the sequence on the probe exactly matches a counterpart sequence on the target DNA/RNA, the probe latches on. The probe is usually chemically bound to a "reporter" molecule, which produces a signal -- often fluorescence -- and advertises the presence of the target sequence.

There is no shortage of applications for DNA probes. Southern blotting detects other DNAs; northern blotting...

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