FISH Basic Method

• Each probe is specific to one region of a chromosome (pair), and is labeled with fluorescent molecules throughout it's length.
• Each microscope slide contains many metaphases.
• Each metaphase consists of the complete set of chromosomes, one small segment of which each probe will seek out and bind itself to.

The first step is to break apart (denature) the double strands of DNA in both the probe DNA and the chromosome DNA so they can bind to each other. This is done by heating the DNA in a solution of formamide at a high temperature (70 C)

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Next, the probe is placed on the slide and a glass coverslip is placed on top. To prevent evaporation, the edges of the coverslip are sealed with rubber cement. The slide is then placed in a 37 C incubator overnight for the probe to hybridize with the target chromosome.

Overnight, the probe DNA seeks out it's target sequence on the specific chromosome and binds to it. The strands slowly rejoin (reanneal).

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Main FISH page

University of Wisconsin - Madison

Waisman Center Cytogenetics Lab