Contained within a 9kb genomic fragment.
Rescues D.melanogaster bw mutant phenotype. The Dvir\bw carried on T(2;3)virilis-bwvar shows variegation, which can be suppressed by Su(var)2-S29D. This variegation can then transinactivate a P{virilis-bw+} element on the homologous chromosome.
Assayed in D.melanogaster.