Test No. 477 : Genetic Toxicology

Mutations in the X-chromosome of Drosophila melanogaster are phenotypically expressed in males carrying the mutant gene. When the mutation is lethal in the hemizygous condition, its presence is inferred from the absence of one class of male offspring out of the two that are normally produced by a heterozygous female. Wild-type males are treated, and mated to appropriate females. The Administration may be oral (solid or liquid), by injection or by exposure to gases or vapours. The numbers of exposure depend on whether the test is: for initial assessment of mutagenicity one exposure or for verification at least three exposure levels. The first generation female is mated individually to their brothers, and in the second generation, the progeny from each separate cross are scored for phenotypically wild-type males. Absence of these males indicates that a sexlinked recessive lethal mutation has occurred in a germ cell of the parent generation male.