Status of the Drosophila melanogaster euchromatic genome. Each chromosome arm is represented by a black horizontal line with a circle indicating its centromere. For each arm, seven tiers of information (A-G) are presented. (A) Each vertical green line represents the position of a transposable element. (B) Each vertical blue line represents the position of a 'declared' gap in Release 2. (C) Each vertical red line represents the position of an 'undeclared' gap in Release 2 greater than 20 bp, detected by comparing the Release 2 and Release 3 sequences. (D) Each vertical black line represents the position of a sequence gap that remains in Release 3. (E) The horizontal bars depict the regions of the genome assigned to LBNL (blue) or the HGSC, Baylor College of Medicine (brown) for generating Release 3. (F) The gray horizontal bar represents the status of the physical maps that supplied the initial BAC tiling paths for sequencing; presence of the gray bar indicates an available BAC contig. The sources of these BAC maps were as follows: chromosome X [12,50], chromosome arms 2L, 2R, 3L, and 3R  and chromosome 4 . The black triangles represent the seven physical map gaps remaining in the euchromatic portion of the genome in Release 3. (G) The purple bar represents the position of cosmid, P1 or BAC clones that had been completely sequenced prior to Release 2. Those at the telomere of chromosome X were sequenced by the EDGP ; the other clones were sequenced by the BDGP at LBNL . The numbers to the left of rows A, B, C and D are the chromosome arm totals for each category plotted. The scale in million bases (Mb) is shown at the bottom of the figure.