The polytene dot chromosome of Drosophila: D. melanogaster and D. subobscura.

The chromosome arms are assumed to be homologous within the genus Drosophila. Homology at the level of the polytene chromosome banding pattern between non-sibling species is, however, almost impossible to establish as different processes such as inversion, transposition and unequal crossing over, have disturbed it. Even though the band sequences cannot be followed, we may ask whether there is a correlation in the total number of bands between species.