SKY Fact Sheet

National Human Genome Research Institute

National Institutes of Health
U.S. Department of Health and Human Services


Spectral Karyotyping (SKY)

Spectral Karyotyping

What is SKY?

Spectral karyotyping (SKY) is a laboratory technique that allows scientists to visualize all of the human chromosomes at one time by "painting" each pair of chromosomes in a different fluorescent color.



What is SKY used for?

Many diseases are associated with particular chromosomal abnormalities. For example, chromosomes in cancer cells frequently exhibit aberrations called translocations, in which a piece of one chromosome breaks off and attaches to the end of another chromosome. Identifying such chromosomal abnormalities and determining their role in disease is an important step in developing new methods for diagnosing many genetic disorders.

Traditional karyotyping allows scientists to view the full set of human chromosomes in black and white, a technique that is useful for observing the number, size and shape of the chromosomes. Interpreting these karyotypes, however, requires an expert, who might need hours to examine a single chromosome. By using SKY, even non-experts can easily see instances where a chromosome, painted in one color, has a small piece of a different chromosome, painted in another color, attached to it.

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How does SKY work?

SKY involves the preparation of a large collection of short sequences of single-stranded DNA called probes. Each of the individual probes in this DNA "library" is complementary to a unique region of one chromosome - together, all of the probes make up a collection of DNA that is complementary to all of the chromosomes within the human genome.

Each probe is labeled with a fluorescent color that is designated for a specific chromosome. For example, probes that are complementary to chromosome 1 are labeled with yellow molecules, while those that are complementary to chromosome 2 are labeled with red molecules, and so on.

When these probes are mixed with the chromosomes from a human cell, the probes hybridize - bind - to the DNA in the chromosomes. As they hybridize, the fluorescent probes essentially paint the full set of chromosomes in a rainbow of colors. Scientists can then use computers to analyze the painted chromosomes to determine whether any of them exhibits translocations or other structural abnormalities.

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Last Updated: October 13, 2011