Table 2 Breakpoints on 2nd chromosome balancers
Balancer(s)Component aberrationPolytene breakpoint1Proximal breakpoint coordinateDistal breakpoint coordinateDuplication (+) or deletion (–)Predicted band2Disrupts
SM1, SM5, SM6a, CyOIn(2L)Cy22D1–2Unknown3Unknown3Unknown22D1CG11723, TBCD, or AIF4
SM1, SM5, SM6a, CyOIn(2R)Cy42A2–32R:6,012,4592R:6,012,739+28042A75′ of Src42A
SM1, SM5, SM6aIn(2LR)SM122A3–22B12L:1,586,8452L:1,586,840−422A3haf, CG10869
SM6a, CyOIn(2LR)O30E–30F2L:9,805,5752L:9,805,567−730D1nAChRα6
  • 1 Breakpoint observed in polytene chromosome preparations (Lindsley and Zimm 1992).

  • 2 Breakpoint position predicted from genomic coordinate using FlyBase correlation table.

  • 3 Breakpoint mapped to the interval 2L:2,146,403–2,156,403.

  • 4 One or none of these three genes may be affected by the breakpoint.

  • 5 Breakpoint mapped to the interval 2L:12,726,221–12,736,221.

  • 6 Because SM5 arose from SM1 through two inversions (In(2L)SM5-1 followed by In(2L)SM5-2) and a complex rearrangement, we have given symbols to these component aberrations to replace the single aberration In(2LR)SM5. The symbol Dp(2;2)SM5 was chosen for the complex rearrangement to emphasize the duplicated segment from the progenitor over the inverted segment.

  • 7 This breakpoint could not be localized molecularly, but recessive lethality presumably associated with the breakpoint was mapped to the interval 2L:8,529,124–8,700,124 by complementation tests with molecularly defined chromosomal deletions.

  • 8 Bands corresponding to the 2L:8,529,124–8,700,124 interval defined by chromosomal deletions.

  • 9 The proximal side of the breakpoint is present in two presumably identical copies juxtaposed to low-complexity sequence and maps to the 2L:6,916,809–6,917,405 interval.

  • 10 The sequence on the distal side of the breakpoint suggests this gene is disrupted.

  • 11 A second, intact copy of this gene is present elsewhere on SM5.