Each spot on this microarray contains a short sequence of DNA that hybridizes to a specific sequence on the gene encoding the normal or mutant form of the cystic fibrosis gene.

Microarrays of DNA sequences can be made on silicon chips such as these, on glass slides, or on a number of other supporting media.

DNA from a patient is broken into short pieces and combined chemically with a fluorescent compound. DNA from the patient binds binds to DNA on the microarray, giving a characteristic pattern of fluorescence.

The next slide shows that patterns from normal and CF patients are easily distinguishable.