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As staining techniques evolved, scientists used them to link chromosome changes to disease: Missing bands indicated a deletion of genetic material, as in some inherited diseases, whereas extra bands, or translocations, indicated altered or additional genetic material, as is the case in many cancers.

Higher-resolution molecular techniques for visualizing chromosome regions, particularly fluorescence in situ hybridization, or FISH, later improved the process. FISH uses DNA probes labeled with fluorescent dyes to identify specific chromosomal regions. Spectral karyotyping is a new way to interpret data from FISH experiments and has distinct advantages over conventional microscopy.

Ried and his coworkers applied spectral imaging, a technology used in remote sensing devices, to chromosomes isolated from cells. First, they applied different molecular "paints" to the chromosomes. The wavelengths of light, or emission spectrum, each painted chromosome emitted provided a unique "thumbprint" for that chromosome. Although to the eye, the thumbprints are difficult to distinguish from one chromosome to the next, computers rapidly detect differences in emission spectra and assign each chromosome its own easy-to-see color. In a spectral karyotype from a healthy cell, for example, computers translate the emission spectrum for chromosome 1 into yellow, chromosome 2 red, 3 gray, 4 turquoise, and so on.

Ried and his coworkers have also showed that spectral karyotyping can be used effectively to pinpoint chromosomal changes linked to disease. They identified structural abnormalities in chromosomes from several different samples obtained from diagnostic laboratories, and demonstrated the value of the technique in identifying a breast cancer cell with a large number of broken and rearranged chromosomes and extra genetic material.

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Contact: David Brand
dbrand@u.washington.edu
206-543-2580
University of Washington
21-Jan-1997