Cryopreservation
Cryopreservation of gametes or embryos from scientifically valuable mice has become increasingly important.
1st of all, once the cryopreserved gametes or embryos are frozen and maintained under liquid nitrogen, they can be theoretically held indefinitely without any adverse effects. The first groups of mouse embryos were frozen in 1972 and thawed 25 years later in 1997 to produce the live pups in Jackson Lab.
2nd, the stored gamtes or embryos in liquid nitrogen offer a safe way to preserve lines with potential future use but no current use, and savings in space and the expense associated with keeping a breeding colony.
3rd, during the process of gamete and embryo collection, most pathogenic organisms are excluded similar to other methods used to rederive lines of mice.