Fluorescence in situ Hybridization (FISH)
A chromosome, which is a molecule of DNA and its associated proteins, may be observed under a microscope with the aid of dyes and probes.
One technique, called fluorescence in situ hybridization, or FISH, permits detection of specific chromosomes, regions of DNA, or RNA transcripts. This is achieved by incubating a sample with highly specific oligonucleotide probes that are fluorescently labeled.
Because these probes may be hybridized to uncondensed chromosomes in non-dividing cells, FISH may be more broadly applied than classical karyotyping methods. Such observations are a powerful approach for detecting defects in chromosome structure and number, which are often associated with diseases and disorders.