The Pattern of R2 Retrotransposon Activity in Natural Populations of Drosophila simulans Reflects the Dynamic Nature of the rDNA Locus
Diagramed at the top is a full-length R2 element with the location of the ORF and 5′ and 3′ untranslated regions indicated. Shown below the R2 diagram are the individual 5′ truncation profiles of each iso-rDNA line. Each horizontal line represents one of the D. simulans lines with the position of the vertical lines indicating the 5′ end point of a truncated R2 element in that line. Because all R2 insertions have an intact 3′ end of the element, each 5′ truncated R2 copy extends from the vertical line to the 3′ end of the R2 element. The collection of the 5′ truncated R2 copies differs for each line. Those 5′ truncations connected by dotted lines are shared between lines with those dotted lines indicated with an asterisk shared between the two populations. Full-length R2 elements in each line can also show small differences in length but are not shown. For each population the lines are arranged from the highest level of R2 transcript (top) to the lowest level of transcripts (see Figure 3).