Nucleic acid hybridisation

Nucleic acid hybridisation is a procedure that involves fishing out a specific nucleic acid - called the target - in a mixture of fragments, by annealing it to a custom-made complementary nucleic acid that is labelled for detection - called the probe.

The procedure involves first denaturing the fragment mixture, which is immobilised on a filter, so that the complementary probe can anneal to its target. This may be done either by heating or alkaline treatment (however RNA cannot undergo alkaline treatment as it is degraded). The labelled probe is then washed over the fragment mixture in vast molar excess under high stringency conditions, and labelling is detected to home in on the location of the target.

Applications of nucleic acid hybridisation include: detecting mutation in a DNA sequence, gene microarrays, screening gene libraries (plaque or colony hybridisation), Southern blot analysis for restriction fragments, Northern blot analysis for RNA size or abundance, and in-situ hybridisation for detecting RNA transcripts in vivo.