About the Cover

About the Cover
The old and the new: in Drosophila, chromosomal aberrations are traditionally mapped at the cytological level by the analysis of polytene chromosomes. New methods, utilizing molecularly mapped transposon insertions, facilitate the construction of custom chromosomal aberrations with breakpoints mapped to the genome sequence at base-pair resolution. The background shows three different deletions heterozygous with wild-type chromosomes, which are visible as missing bands or bulges (gray arrows). The foreground shows a set of 177 precisely mapped deletions generated by the DrosDel consortium, covering the majority of chromosome 2L. Using the DrosDel P-element insert collection, a set of 655 deletions covering 77% of the fly genome has been made. Combining DrosDel elements with other mapped FRT sites allows construction of >500,000 deletions covering almost 99% of the fly genome. The fly stocks and computational tools developed by the DrosDel team increase the sophistication with which the fly genome can be manipulated since, along with deletions, precisely mapped duplications and inversions can also be easily generated (see RYDER et al., pp. 615–629).