Chromosomal Aberrations in Drosophila ananassae

Abstract

In D. ananassae, different types of chromosomal rearrangements, like paracentric and pericentric inversions, transpositions, translocations, extrabands, and deficiencies, have recurrently been found in natural populations, but these chromosome rearrangements are rarely found in other species of Drosophila, thus reflecting high mutability in D. ananassae. A large number of inversions are the common feature of D. ananassae genome. A total of 76 paracentric inversions, 21 pericentric inversions, and 48 translocations so far have been reported in the populations of D. ananassae. Paracentric inversions are the predominant feature of D. ananassae genome. Majority of these paracentric inversions have limited distribution and are transient in nature except three cosmopolitan inversions, namely, Alpha (AL) in 2L, Delta (DE) in 3L, and Eta (ET) in 3R, which show worldwide distribution. The presence of pericentric inversions and translocations are among the most unusual features of natural populations of D. ananassae. A given arrangement may occur in one region but may be absent in other. An explanation to account for such disjunct distribution of gene arrangements may be that all types of arrangements did not occur simultaneously in the past history of the species. The former types, being older, had greater opportunities for migration and thereby at present they have a distribution throughout the world. On the contrary, those rearrangements of relatively recent origin and due to obvious impediments in the means of migration could not migrate from their respective native place to the localities where they have been found wanting.