Enzymes are cleaving the substrate. If the substrate is DNA they are called restriction enzymes. Activating enzymes will cut off the domain that is biological active to become functional.
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Rats are used to make rat monoclonal anti mouse antibodies. There are less rat- than mouse clones however. Rats genes from rodents of the genus Rattus norvegicus are often studied in vivo as a model of human genes in Sprague-Dawley or Wistar rats.