There is a war going on to win over the hearts and minds of molecular biologists: Radioactive isotopes-long the gold standard for tagging and later detecting RNA and DNA strands- are being challenged by a new generation of fluorescent labels that promise greater flexibility with fewer disposal problems.

SEQUENCE DETECTION SYSTEM: Perkin-Elmer’s ABI Prism 7700 system uses a probe with a reporter and a quencher dye attached to it.
With 14C, 32P, 125I, 3H, or some other radioactive atom built into the phosphorous backbone, ribose, or bases of DNA or RNA sequences (oligonucleotides), radiolabeled oligonucleotides are easily quantified using a Geiger counter or by the signature they produce on the grains of silver halide in a photographic emulsion.

That endearing quality helped boost radiolabels to the forefront of molecular biology techniques. Labeled oligonucleotides will pair with complementary stretches according to the Watson-Crick model: Guanine on one chain links to a...

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