Gene frequencies in natural and laboratory populations of Drosophila nasuta

Gene arrangement frequencies of different chromosome types of three inversions, IIL-2, 111-35 and 111-2 are reported in some natural and laboratory populations of Drosopfrila nasurn. In general, the frequencies of inversion heterozygotes for these inversions are in excess of what is expected under Hardy-Weinberg equilibrium in both natural and laboratory populations. This suggests that these inversion heterozygotes are heterotic to the species as far as viability is concerned. Similar to what occurs in the cosmopolitan species, chromosomes with standard gene sequences are more frequent than inverted gene sequences in this species. The scarcity of inversion homozygotes is due to reduced viability of their carriers, which probably have lethal or sublethal combinations of alleles in the inverted sections of their chromosomes. Further, the inversion frequencies in laboratory populations follow the frequencies in natural populations.