A number of mutations, including zb*-143, zn*-143, al*-143, and j*-220, have been isolated during the genetic examination of the heterochronic mutation Cg2 (MNL 1992). The latter is allelic to j1 on 8L. Chlorophyll mutations, with longitudinal yellow stripes on leaves that are phenotypically similar to ys, are constantly appearing during reciprocal hybridization of some substocks. The tests for allelism have shown that ys*-308, ys*-309, ys*-310, and ys*-253 are allelic to each other (Table 1). Both ys*-308 and ys*-309 are allelic to ys3 on 3L, but ys*-310 and ys*-253 are not. Only one allele, ys*-9196 from the ys br stock, turned out to be allelic to ys on 5L.
The high frequency of this mutation appearing in the genetic background of stock carriers of the Cg2 and Cg2+ alleles might be associated with either the activity of the mutation systems that are widely used in transposon tagging (Ac and En) or a new mutator system, the TE (transposable element) of which is located on the short arm of chromosome 9 in sites adjacent to the Wx locus.
Table 1. Tests for allelism between different ys alleles.
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