Activity variants of acid phosphatase-3 among chromosome 3 inversions of Drosophila pseudoobscura.

Allozymes of the Ap-3 locus in Drosophila pseudoobscura show very strong associations with chromosome 3 inversions. The 0.98 electrophoretic allele is associated with The TL, SC, CH and PP gene arrangements, while the 1.00 electrophoretic allele is characteristic of the AR and ST gene arrangements. Variation in relative 0.98 and 1.00 AP-3 allozyme activities of chromosome 3 isogenic strains was examined on acrylamide gels in F1 heterozygotes obtained by crossing these strains individually to a reference strain with a slower 0.87 mobility allozyme. F2 analyses demonstrated that the activity variants co-segregate with the Ap-3 locus. Both 0.98 and 1.00 allelic classes are polymorphic for AP-3 activities. In contrast to the virtual monomorphism for an electrophoretic allele, each inversion is polymorphic for AP-3 activities. These results reveal substantially more genetic differentiation among gene arrangements than is evident from electrophoretic allele comparisons. Strains having the PP arrangement are distinct from TL strains in their AP-3 activity expression, and ST strains have a wider range of variation than AR strains. In contrast, no geographical differentiation is evident for strains from the Bogota population of D. pseudoobscura.