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

Abstract

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. The polytene dot chromosome is an excellent starting point for such an approach. Here we present the detailed cytology of polytene chromosome 4 of D. melanogasterand the polytene dot chromosome of D. subobscura using electron microscopy. The results show that the number of bands is about the same, around 30, in both species. We predict that by using thin sections and electron microscopy for the longer polytene chromosome arms, both species will turn out to have approximately equal band numbers.

Molecular and genetic organization of bands and interbands in the dot chromosome of Drosophila melanogaster

“…1c–e); therefore, this number is considered to be unjustifiedly overestimated (Saura et al 2002). In addition, according to Hochman and Slizynski, the fourth chromosome has a polytenized left arm (King 1975; Slizynski 1944); however, it is unclear whether this structure is indeed a 4L chromosome or an ectopically attached portion of another chromosome (Saura et al 2002). The map by C. Bridges (Bridges 1935a; Fig 1…”

“…1a, b), electron-microscopic photograph of V. Semeshin (Fig. S1b), and band names from Saura et al (2002). We made the resulting cytological map of the fourth chromosome based on the map by C. Bridges (1935a), band numbers by Saura et al (2002), and our mapping efforts (Fig.…”

Sequence signature analysis of chromosome identity in three Drosophila species

“…Images were assembled, contrasted and merged electronically using Adobe Photoshop. Well spread F-elements were mapped according to Saura et al [45] and POF-binding regions were defined. To correlate cytological positions to sequences we used the Dm genome release 3.2.…”