The production of visible mutations inDrosophilaby chloroethyl methanesulphonate (CB 1506)

Abstract

The claim that CB 1506 produces an unusually high proportion of visible to lethal mutations could not be confirmed. The ratio of visible to lethal sex-linked mutations was less than 1:10 in bothMuller-5and attached-X tests. In one brood it rose to 1:5 when unconfirmed visible mutants were included. The much higher ratio obtained by Fahmy and Fahmy is interpreted as a methodological artifact, due to the inclusion in their calculations of mosaic visibles but not of mosaic lethals.Two visible mutations—twisted abdomen andwsatsuma—occurred more than once. This suggests the possibility of a locus or allele specific effect of CB 1506.