Polytene chromosomes normal.
Su(z)21.a5 shows no dominant effect on telomeric Position Effect Variegation (PEV) in stocks carrying a variegating w+mW.hs allele at the telomeres of the second and third chromosome.
Isolated on the basis of reverting the dominant z1 eye color suppression associated with Su(z)21. In a z1, wis/Y background, Su(z)21.a5 produces an orange eye colour similar to that found in z1, wis/Y;+/+. The reversion event simultaneously reverted the ability of Su(z)21 to enhance the dominant loss of chaetae phenotype associated with Su(z)2vg62 (Df(2R)vg62) and Su(z)2vgD (Df(2R)vg-D). Heterozygotes with Df(2R)vg-D are viable. Hemizygotes die as larvae/pupae.