ABSTRACT
Fluorescence in situ hybridization (FISH) is in general single cell–oriented; single to multiple loci in a genome can be accessed by single to multicolor-FISH approaches. Repetitive and/or heterochromatic DNA stretches can be easily visualized by FISH. Locus-specific probes (LSPs) are normally euchromatic DNA-stretches cloned into genetic vectors; nowadays in most cases bacterial artificial chromosome clones are used as basis for LSPs. FISH is normally used to access single cells. However, when doing comparative genomic hybridization, the single cell–derived metaphase chromosomes of a normal individual is just used as a kind of matrix, or low-resolution DNA-chip. LSPs and/or repetitive probes are the probes normally being applied in molecular combing, where FISH is possible in almost base pair resolution on maximally stretched DNA-fibers. However, it soon became apparent that the FISH concept offered promising possibilities also in a number of other areas in biology and its use spread into new areas of research and also into the area of clinical diagnosis.
