Fig 3.

Variable structure of Penelope copies isolated from the transformed D. melanogaster subline A1. (A) The reference original Penelope clone p6. (B–E) Penelope elements isolated from phage libraries. (F) An intronless Penelope element (solo LTR) isolated from a plasmid library. Elements D and E are Sau3A, are truncated at the 5′ end, and have an additional 20-bp sequence at the 3′ end that was derived from flanking sequences present in the original construct. Element C has an additional 34-bp repeat at the very beginning of the Penelope ORF. This 34-bp repeat was also detected at the 3′ end of some Penelope copies cloned from D. virilis. In clones B and C, the junction between the sense and antisense sequences is 6 nt upstream of the BamHI site, ruling out the possibility of a cloning artifact. Restriction enzyme abbreviations: B, BamHI; E, EcoRI; S, Sau3A; X, XhoI.