Researchers have been using "Fluorescence in situ hybridization" (FISH) analysis for decades to literally fish for specific DNA and RNA sequences in intact cells and tissues within their vast seas of nucleic acid molecules. Because of its ability to light specific sequences up under the microscope at the exact locations at which they reside, FISH has come to be a go-to method in the diagnosis of chromosomal abnormalities, investigation of the 3-D organization of genomes in cells' nuclei, analysis of the immediate products of gene expression known as messenger RNAs and more.
* This article was originally published here
