FISH

FISH, flourescent insitu hybridization is a molecular technique used to visaulize expression patterns of genes in a model organism. Knowing where a gene is expressed can give clues as to what role the gene plays in the organism. In fluorescent in situ hybridization, a fluroescent RNA probe is made and introduced into the organism, where it binds the appropriate gene sequence. As you can guess, the sequence of the RNA probe has to be complementary to that of the desired DNA sequence. Probe generation involves DNA extraction, polymerase chain reaction (PCR) to amplify the desired sequence, and then in-vitro transcription to turn DNA to RNA. The probe then has to be labeled. The actual in-situ hybridization process varies depending on the model organism used. In zebrafish, the whole process last about 4 days. The image of the expression pattern can be obtained by using confocal microscopy.