A new FISH protocol with increased sensitivity for physical mapping with short probes in plants

Fluorescence in situ hybridization (FISH) is a well-established technique u sed for the detection of specific DNA regions, that has been applied to int erphase nuclei, pachytene and metaphase chromosomes as well as to extended DNA fibres. This technique allows the physical mapping of specific DNA sequ ences both on individual chromosomes and extended fibres. A new FISH protoc ol is described here that enhances the sensitivity of the method. Probes fo r small unique DNA sequences of less than 2 kb give high signal-to-noise ra tio with this method, and can be visualized easily by means of conventional fluorescence microscopy.