The 2R:12200815..12278809 release 6 coordinates of the left breakpoint are estimates. The left extent corresponds to the right end of RpS11, because Df(2R)CB21 heterozygotes do not show the Minute phenotypes associated with deletion of this haploinsufficient gene. The right extent corresponds to the right end of Cam, which published results say is deleted.

The 2R:12453190..12530888 release 6 coordinates of the right breakpoint are estimates. The left extent corresponds to the left end of Lac, which published results say is deleted. The right extent corresponds to the estimated position of the left end of polytene band 49B1, because the published cytology indicates this breakpoint lies in subdivision 49A.

The Df(2R)CB21 chromosome acts as a dominant moderate suppressor of telomeric silencing (assayed using the effect of the chromosome on the eye colour phenotype of flies carrying "P{w^var}KR3-2", a stable "brown-red" variant of the P{3'WP-2,w^var}2Lt insertion), but this is a false positive result (the suppressor is not within the bounds of the deficient region) because the suppressor maps to the tip of 2L rather than to the site of the deficiency. In addition, the deficiency chromosome fails to complement lethal mutations of l(2)gl; deficiencies that are mutant for l(2)gl are often also deficient for the 2L TAS array (FBrf0137248) and it has previously been shown (FBrf0137248, FBrf0158986) that partial or complete deficiency of the 2L TAS array on the homologue suppresses silencing of brown-red variants of P{3'WP-2,w^var}2Lt.

γ ray induced deletion of a P-element inserted at 49A.