Df(3R)rn20 shows both "rn" and "roe" phenotypes.

The testes of homozygous males appear generally less full than wild-type testes and contain large, vacuolated oval bodes which are often densely staining. Fibrous flagella are clearly visible within these giant cysts, but the seminal vesicles are empty. The testes contain large round tissue masses, in contrast to the thin long cysts present in wild type. Spermatid tails appear clumped along much of their length in the testes of mutant males. Isolated mutant testicular cysts show no changes in the cyst head region compared to wild type, but more distally the cysts show aberrant terminations and are shorter than normal, with less than 10-15% exceeding even a third of the normal length. The tails of the abnormal cysts are several times the normal diameter and they terminate in a "ball-of-yarn" configuration which is composed of masses of intertwined spermatid flagella. F-actin staining is homogeneous in the mutant testis cysts, with no localised accumulations corresponding to the individualization complexes seen in wild-type testes. The spermatids are randomly oriented in the mutant cysts, being separated by an excess of granular cytoplasmic material. Mitochondrial condensation is also abnormal, as portions of the major mitochondrial derivative are incompletely retracted. High numbers of spermatids are present within a single cytoplasm without intervening membranes in mature mutant cysts.

Homozygotes show a severe disruption in the internal organisation of the retina; a reduced number of ill-defined ommatidia are randomly dispersed in a nondescript vacuolated substance with some dispersed membrane. Few photoreceptor cells are seen, rhabdomeres are malformed and some irregularly disposed pigment cells are present.

Homozygotes have small rough eyes. Df(3R)rn20/+ flies have normal eye morphology.

Dominant enhancer of the gl³ phenotype.