The genetics of Drosophila subobscura populations. V. A study of linkage disequilibrium in natural populations between genes and inversions of the E chromosome.

The genetics of Hk and Est-9 complex gene have been studied in Drosophila subobscura. While Hk alleles mendelize normally, Est-9 is a complex locus consisting of several very closely linked genes with active and silent alleles. Both genes are located on chromosome E; a detailed genetic map was constructed with the help of visible markers and inversions. Both Hk and Est-9 are included in or are very near to inversions of the E chromosome. While Hk does not show linkage disequilibrium either with Est-9 or inversions, Est-9 does show disequilibrium in two ways: both with inversions and between different Est-9 genes. All natural populations studied show the same kind of association between Est-9 gene combinations and inversions. It is argued that these results are better explained by selection than by neutrality.