Drosophila mediopunctata
belongs to the tripunctata group, and is one of the commonest
Drosophila
species collected in some places in Brazil, especially in the winter. A
standard map of the polytene chromosomes is presented. The breakpoints of
the naturally occurring chromosomal rearrangements are marked on the map.
The distribution of breaking points through the chromosomes of
D. mediopunctata
is apparently non-random. Chromosomes X, II and IV show inversion polymorphisms.
Chromosome II is the most polymorphic, with 17 inversions, 8 inversions
in the distal region and 9 in the proximal region. Chromosome X has four
different gene arrangements, while chromosome IV has only two.
