Biology. A strain is called inbred when it has been mated brother and sister for 20 or more consecutive generations. An inbred strain has a unique genotype and consequently a unique phenotype. Specific strains have been developed for a high incidence of tumours, specific immune responses, unique pattern of behaviour, susceptibility to spontaneous diseases and other characteristics. Although more expensive than outbred animals, inbred animals have properties which make them useful and sometimes essential in many research areas, especially in cancer research. A commonly used inbred strain is the Fischer 344 rat.
Compare to outbred.