A note on some alleles of aristapedia

Abstract

1. Larvae homozygous for several alleles of aristapedia (ss a, ssaB, ssa40a andss aSnB) were transferred for three days to 18°C. after being kept at 27°C. for 12,24,36,48 or 60 hr. from laying. They were then scored for the grade of transformation of the arista into a tarsus and for the distortion of the normal tarsus. In all cases both the abnormalities were increased by cold treatments given after 48 or 60 hr. 2. The patterns of effect were similar inss a40a andss aSnB, both of which always have a strong aristal effect and in the higher grades a strong tarsal effect;ss aSnB is always stronger thanss a40a under the same conditions. 3. A different pattern is characteristic ofss a, which has a strong aristal effect and a weak tarsal effect. The pattern is different again inss aB, which at high temperature has a weak effect, and at low temperature a moderate effect, on both aristae and tarsi. 4. The existence of these different patterns of effect shows that the alleles are not related in a simple quantitative manner, but differ qualitatively. 5. In flies homozygous for alleles which have strong effects on both organs (i.e.ss a40a andss aSnB) the aristal tarsus may be stunted just as is the leg tarsus. This demonstrates that the effect of the gene is not produced by a simple growth stimulation.