Dsub\gypsy elements lack functional env proteins due to frame-shifting mutations in this region, consequently these elements lack infective ability. This suggests Dsub\gypsy is a degenerate form of insect retrovirus.

The nucleotide sequence of Dsub\gypsy is determined. A comparative analysis of the sequence and molecular structures of Dsub\gypsy, Dvir\gypsy and gypsy reveals gypsy is the only infectious particle, the other two have lost the ability. gypsy elements are found in D.subobscura natural populations suggesting the populations were invaded by infectious gypsy elements.

Dsub\gypsy, Dvir\gypsy and gypsy show many structural similarities including sequences necessary for transcription and regulatory and coding sequences which suggest a common mechanism of expression. The ORF3 of Dsub\gypsy and Dvir\gypsy lack some motifs essential for the function of the "env-like" protein.

Sequences homologous to the gypsy element are well conserved among species of the obscura subgroup.

Comparisons between gypsy sequences in D.melanogaster, D.subobscura and D.virilis strongly suggest that gypsy sequences have been horizontally transferred between these species.

Dsub\gypsy shows close sequence similarity to its D.melanogaster homolog.