Isoenzyme frequencies in long-term selection lines of Drosophila melanogaster: IV. Isoenzyme frequencies of the leucine aminopeptidases (LAP) in lines selected for short and long developmental rate.

1. Selection lines derived from a reference line, the continuation of an initial population which were founded by a double cross of four laboratory stocks, were selected for short (line KS and K) and long (line LS and L) developmental rate for up to 183 generations. 2) Frequencies of the linkage groups, A(O)D(F) , A(F)D(F) and A(S)D(S) , of two closely linked loci, LAP-A and LAP-D, were estimated by frequencies of the isoenzymes controlled by them. 3) The reference line RE had maintained a balanced allele polymorphism for all three linkage groups with the frequencies f(A(O)D(F))=0,145; f(A(F)D(F))=0,605; and f(A(S)D(S))=0,250. The reference line differs from the four laboratory stocks in which two further linkage groups (A(O)D(S) and A(S)D(F)) occur. 4) Both lines selected for short developmental rate are different from each other and from the reference line. While in line K the linkage group A(O)D(F) was fixed, in line KS the linkage groups A(F)D(F) and A(S)D(S) maintained a balanced polymorphism. 5) The lines selected for long developmental rate LS and L are distinct from the reference line, too. In both lines the linkage groups A(O)D(F) and A(F)D(F) are present. They differ from each other by a higher frequency of linkage group A(O)D(F) and a smaller one of linkage group A(F)D(F) in line LS. 6) The discussion mainly deals with the influence of the three following aspects: the response of the selection lines to selection; the mechanisms maintaining allele polymorphism; and the genetic drift.