Electrophoretic variations of prophenoloxidase were obtained from natu
ral populations of Drosophila melanogaster. A1, one of the 2 isoforms
of the prophenoloxidases, is polymorphic: 10 fast-migrating and 2 slow
-migrating types were found in polyacrylamide gel electrophoresis amon
g 271 wild strains. The majority were the intermediate-migrating type.
By use of these variants, A1 gene was mapped at 79.6 on the right arm
of the second chromosome. By deletion mapping, its cytological positi
on was located at 55A-B. In the electropherograms, hybrids between the
types differing in mobility exhibited 3 bands, indicating that A1 is
a dimeric protein. The gene for A1 is expressed through larval, pupal
and adult stages.