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 procedure for the cryopreservation of Drosophila melanogaster
embryos has recently
been developed. Cryopreservation of D. melanogaster is of special
interest to geneticists and
evolutionary biologists because it would make it possible to assay control
and experimental
populations simultaneously during long-term studies. Before cryopreserved
embryos can be used
for such studies, it is first necessary to show that cryopreservation
is not mutagenic. We tested for
mutagenic effects of cryopreservation 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 does not increase mutation
by a factor greater than 2·39.
This is the first quantitative estimate of the mutagenic effect of
cryopreservation on the germ line
of a metazoan. The results are reassuring when considering the genetic
impact of cryopreservation on mammalian gametes and embryos.