FISH Basics

In the FISH process, fluorescent dye molecules are bound to DNA segments (probes) that are complementary to specific regions of DNA on a chromosome.  When the probe and patient DNA are mixed and allowed the hybridize, the probe DNA binds to the patient DNA if the proper sequence is present.  Since there should be two copies of every gene region, two copies of each probe signal (orange and green) should be seen during analysis.