A strain is defined as inbred when it has been mated brother x
sister for 20 or more consecutive generations (F20). All offspring
can be traced back to a single ancestral breeding pair in the 20th
or subsequent generation. Such inbred strains are therefore
isogenic (genetically identical). At Harlan Laboratories, these
colonies are maintained as Foundation Colony (FC), Pedigreed
Expansion Colony (PEC), and Production Colony (PC). Offspring from
the FC provide breeders to the FC and PEC; offspring from the PEC
provide breeders for the PC. Offspring from the PC are supplied to
researchers.
Each inbred strain has a unique genotype and consequently a unique
phenotype. Phenotypical differences between inbred strains should
be taken into account when designing experiments. Specific strains
have been developed for a high incidence of tumors, unique pattern
of behavior, specific immune responses, susceptibility to
spontaneous diseases and other characteristics. Inbred strains have
been used in cancer research for over 60 years. Although somewhat
more expensive than outbred animals, they have properties which
make them useful and essential in many types of research.
Nomenclature of inbred strains is designated by one or more capital
letters(s), followed by abbreviated name(s) or breeder(s), to
include transfers. For example: C57BL/6NHsd.