rat strain hybrid strain 2010-01-11T12:00:00Z 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. RS:0002067 rat_strain_ontology rnigam