ANALYSIS OF SPONTANEOUS AND ETHYLMETHANSU LPHONATE-INDUCED VISIBLE MUTATIONS IN THE GENETICALLY UNSTABLE MS, W STRAIN OF DROSOPHILA-MELANOGASTER

We analyzed genetic effects of ethylmethansulphonate (EMS) on mature s perm of males of the Drosophila melanogaster MS, w strain. The frequen cy of induced mutations was estimated in the X chromosome, in five loc i of chromosome 2 (b, j, pr, cn, and vg), and in eight loci of chromos ome 3 (ru, h, th, st, cu, sr, e(s), and ca), Mutability was significan tly increased in the genetically unstable MS, w strain in comparison w ith the reference laboratory ss, w strain. In MS, w, genetic instabili ty was characteristic of more than 50% of EMS-induced mutations. Analy sis of the mutation spectrum revealed a specific distribution along th e chromosomes. In MS, w, exhibition of spontaneous and induced instabi lity was shown to be similar. This could imply a common mechanism of c ontrol of mutability involving transpositions of mobile genetic elemen ts.