Epitope tags are short peptide sequences that are easily recognized by tag-specific. Due to their small size, epitope tags do not affect the tagged protein's biochemical properties. Most often sequences encoding the epitope tag are included with target DNA at the time of cloning to produce fusion proteins containing the epitope tag sequence. This allows epitope tag to serve as universal detection reagents for any tag containing protein produced by recombinant means. This means that epitope tags are a useful alternative to generating specific to identify, immunoprecipitate or immunoaffinity purify a recombinant protein. The epitope tag is usually functional in a variety of dependent experimental procedures. Expression vectors producing epitope tag fusion proteins are available for a variety of host expression systems including bacteria, yeast, insect and mammalian cells.