A strain that is essentially homozygous at all genetic loci. In mice, such strains are produced by brother–sister mating for at least 12 sequential generations, or more if other breeding systems are used.

A group of organisms so highly inbred as to be genetically identical, except for sexual differences.

A set of animals produced by at least 20 consecutive generations of sister x brother or parent x offspring mating and can be traced to a single ancestral pair in the 20th or subsequent generation. Animals of an inbred strain are nearly fully homozygous, which thus provides a defined and consistent genotype for analysis.

Animals that result from the process of at least 20 sequential generations of brother-sister matings. This process is called inbreeding. [Source: NHBLI/NCBI Glossary

Linear animals or inbred strains are animals of a particular species which are nearly identical to each other in genotype due to long inbreeding. Mating of brother-sister pairs for 20 generations will result in lines that are roughly 98% genetically identical, usually sufficient to be considered an inbred strain (compare to identical twins or clones which are 100% genetically identical, or fraternal twins or normal siblings, which are roughly 50% identical). Such animals are frequently used in laboratories for experiments where for reproducibility of conclusions all the test animals should be as similar as possible.