Spectral Karyotyping

In spectral karyotyping, the chromosomes or chromosomal segments are hybridized with probes of fluorescent dyes in a combinatorial manner. Five dyes (Cy2, Spectrum Green, Cy3, Texas Red, and Cy5) provide enough combinatorial possibilities to “paint” each chromosome with a different color or shade. Although the naked human eye cannot distinguish these different hues, by the use of optical filters, Sagnac interferometer, a CCD camera, and Fourier transformation, it was possible to discriminate the special differences in standard classification colors using a computer program. The approach permitted classification of translocations that were not identifiable by other staining techniques. The lowest limit of differentiation by this technology is 500 to 1500 kbp. The procedure is applicable to clinical laboratory testing and evolutionary analyses. (See also Schröck E et al 1996 Science 273:494; chromosome painting, FISH, GISH; http://www-ermm.cbcu.cam.ac.uk/0000199Xh.htm).