Sperm cryopreservation involves the isolation of mature sperm for the caudal epididymis followed by the cooling, then rapid freezing of sperm in liquid nitrogen. Sperm can be thawed at a future date and incubated with oocytes to generate embryos that are then surgically transferred into recipient females to recover the line.
Sperm cryopreservation is a fast and inexpensive method for preserving germplasm as compared to preserving embryos. Recent modifications to the sperm cryopreservation procedure have vastly improved the quality of thawed sperm, particularly for C57BL/6 and Balb/c strains. Even with these improvements, the fertilization capacity of thawed sperm can vary significantly among mouse lines. However, a substantial amount of material (ie, ~30 x 106 sperm/male) can easily and quickly be isolated and preserved. Sperm from either homozygous or hetero/hemizygous males can be cryopreserved. Bear in mind that when sperm is frozen down, of course, only half the genome is preserved.
We use the same techniques and methods used by Jackson Laboratories.