FISH (Fluorescence In Situ Hybridization)

FISH (Fluorescence In Situ Hybridization) is a special test that can detect and locate specific chromosome regions.

The targeted chromosome region “lights up” if it is present, due to a fluorescent tag.

FISH can be used to help scientists learn if a chromosome region is present or absent in a sample, and if it is in its proper position or not.

FISH therefore can help us learn about the number and structure of certain chromosome regions, including the regions at the ends of chromosome 20, which are arranged in a different structure and may be missing if someone has r(20).