Oligo nucleotide is a single stranded a short DNA fragment generally ranging in size from 20-50 bases. The probes are chemically synthetic and generally end-labeled with hapten.

 

Bacteria from the insect gut:

 

Blue is stained with DAPI.

Red is by CY3 labeled FISH probe.

Further information:

http://www.slh.wisc.edu/cytogenetics/procedures/fish/index.php

http://www.ice.mpg.de/bol/equipment/fish.htm