[Genes and chromosomes: imaging in genetics]

FISH methodologies have made spectacular progress and found wide applications in several areas of clinical studies and research. These techniques are successfully used for visualisation of specific DNA sequences in metaphase chromosomes and interphase cells making this approach, with appropriately chosen probes, a useful adjuvant to conventional cytogenetics in the study of chromosome abnormalities. Improvements have been made in probe generation, developments of new fluorochromes, combinatorial and ratio labelling for multicolor signals and novel hybridization targets as extended DNA. By varying the probe and the target in fluorescence hybridization, numerous applications are being implemented in many fields of human genetics, from clinical cytogenetics to the identification and study of genes involved in monogenic disorders and oncogenic rearrangements.