A simple and rapid method for constructing ring-<Emphasis Type="Italic">X</Emphasis> chromosomes in <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>

Ring chromosomes are of basic interest to the geneticist and cell biologist who study their behavior in meiotic and mitotic divisions. In addition, the mitotic instability associated with some ring-X chromosomes has proven useful in Drosophila as a means to produce gynandromorphs for developmental studies. We describe a method to construct ring-X chromosomes in Drosophila via I-CreI-mediated exchange in rDNA, and then rapidly diagnose the recovery of ring chromosomes via FLP-mediated sister chromatid exchange within the ring. The method we describe provides a ready means to tailor the genetic content of ring-X chromosomes, making it suited to produce ring-X chromosomes for a variety of experimental purposes.