Wing Somatic Mutation and Recombination Test

The Drosophila wing somatic mutation and recombination test (SMART; also known as the wing spot test) provides a rapid means to assess the potential of a chemical to induce loss of heterozygosity (LOH) resulting from gene mutation, chromosomal rearrangement, chromosome breakage, or chromosome loss. This bioassay makes use of the wing-cell recessive markers multiple wing hairs mwh , 3–0.3) and flare (flr ³ , 3–38.8) in transheterozygous mwh +/+ flr ³ animals. When a genetic alteration is induced in a mitotically dividing cell of a developing wing disc, it may give rise to a clone(s) of mwh and/or flr ³ cells (i.e., a “spot”) visible on the wing surface of the adult fly. The total number of clones induced in a group of chemically treated flies gives quantitative data concerning the whole genotoxic activity of a compound, whereas the types of clone can reveal the mutational mechanisms involved in clone production. Variations on the SMART system described in this chapter have been used to measure frequencies of spontaneous LOH in mutants defective in meiotic recombination and disjunction, DNA repair, and cell proliferation (1 –3 ).