Abstract
Biotinylated probes for in situ hybridization (ISH) are now widely used to detect RNAs and viral genomes at the light and electron microscopic levels. Many protocols for ISH with biotinylated probes are now available. The most critical parameters that influence sensitivity and specificity of the procedure are the nature of the probe, the mode of fixation or incorporation of biotin, and the mode of detection of biotin. Biotin can be detected with antibodies or with avidin (or streptavidin) to which is coupled a marker that can be identified under the microscope. Here we review the protocols, pitfalls, advantages, and disadvantages of biotinylated probes for ISH.