Spontaneous Mutation Rate in Drosophila

Abstract
The fre-quency of spontaneously occurring lethal mutations in the X-chromosome of the Sw-b stock of D. melanogaster, as determined by the ClB method, was found to be higher among spermatozoa of previously unmated cf cf 16 to 17 days, and 32 to 33 days after emergence, than among 1- to 2-day-old [female][female].