Another technique for cytogenetic analysis is fluorescence in situ hybridization (FISH). This technique utilizes DNA probes that are specific to regions of individual chromosomes. The probe attaches to the spread of chromosomes from a cell, then a fluorescein stain is applied. This "paints" the chromosome so that it is visible with the aid of a fluorescent microscope. In the example diagram above, the chromosome 21 pair have been painted.

---