The Rat Strain Ontology (RS) is currently being developed at the Rat Genome Database. For more information about this vocabulary or to request additions or changes, please contact us (http://rgd.mcw.edu/contact/index.shtml).
Hybrid strains are the progeny of two inbred rat strains, crossed in the same direction. F1 hybrids are genetically identical. Further crosses produce offspring that are no longer genetically identical, but it may still be appropriate to give them designations reflecting their parentage, similar to those for F1 hybrids.