Inbred strain

Inbred strains (also called inbred lines, or rarely for animals linear animals) are individuals of a particular species which are nearly identical to each other in genotype due to long inbreeding. A strain is generally defined to be inbred once it has undergone at least 20 generations of brother x sister or offspring x parent mating, at which point at least 98.6% of the loci in an individual of the strain will be homozygous.

Experiments in mice have shown some heterozygosity can still be measured until the 40th generation. Some inbred strains have been bred for over 150 generations, leaving individuals in the population to be isogenic in nature.

Inbred strains of animals are frequently used in laboratories for experiments where for the reproducibility of conclusions all the test animals should be as similar as possible. However, for some experiments, genetic diversity in the test population may be desired. Thus, outbred strains of most laboratory animals are also available, where an outbred strain is a strain of an organism that is effectively wildtype in nature, where there is as little inbreeding as possible.

Certain plants including the genetic model organism Arabidopsis thaliana naturally self-pollinate, which makes it quite easy to create inbred strains in the laboratory (other plants, including important genetic models such as maize require transfer of pollen from one flower to another).