We have cloned a 7 kb genomic fragment containing the dominant female-sterile mutation ovoD1. This fragment confers to transgenic females a sterility phenotype, the severity of which depends both on the genetic background and the ratio of ovoD1 product to ovo+ product. Females containing two copies of the ovoD1 transgene, or those containing one recessive null allele at the ovo locus, are about as sterile as ovoD1 females. Twenty transformed strains were obtained and five of them were tested and shown to be excellent tools for identifying a germline clone of cells sustaining mitotic recombination on the autosomes. One of the tested strains carries an insert on chromosome 4, which enabled us to show that mitotic recombination on that chromosome is not a rare event: it is in fact frequent enough for the maternal effects of the zygotic lethal mutations cubitus interruptus Dominant (ciD) and l(4)29 to be studied.