THE EFFECT OF CRYOPRESERVATION ON THE LETHAL MUTATION-RATE IN DROSOPHILA-MELANOGASTER

Although cryopreservation is routinely used for the storage of a range of biological organisms, few studies have been conducted to determine whether cryopreservation increases the frequency of mutation. A proce dure for the cryopreservation of Drosophila melanogaster embryos has r ecently been developed. Cryopreservation of D. melanogaster is of spec ial interest to geneticists and evolutionary biologists because it wou ld make it possible to assay control and experimental populations simu ltaneously during long-term studies. Before cryopreserved embryos can be used for such studies, it is first necessary to show that cryoprese rvation is not mutagenic. We tested for mutagenic effects of cryoprese rvation in D. melanogaster embryos with an X-linked, recessive lethal assay. The mutation rates of cryopreserved and control flies were not significantly different. We can be 95% certain that cryopreservation d oes not increase mutation by a factor greater than 2.39. This is the f irst quantitative estimate of the mutagenic effect of cryopreservation on the germ line of a metazoan. The results are reassuring when consi dering the genetic impact of cryopreservation on mammalian gametes and embryos.