DNA ORGANIZATION AND POLYMORPHISM OF A WILD-TYPE DROSOPHILA TELOMERE REGION

Telomeres at the ends of linear chromosomes of eukaryotes protect the chromosome termini from degradation and fusion. While telomeric replic ation/elongation mechanisms have been studied extensively, the functio ns of subterminal sequences are less well understood. In general, subt erminal regions can be quite poly morphic, varying in size from organi sm to organism, and differing among chromosomes within an organism. Th e subterminal regions of Drosophila melanogaster are not well characte rized today, and it is not known which and how many different componen ts they contain. Here we present the molecular characterization of DNA components and their organization in the subterminal region of the le ft arm of chromosome 2 of the Oregon RC wildtype strain of D. melanoga ster; including a minisatellite with a 457 bp repeat length. Two disti nct polymorphic arrangements at 2L were found and analyzed, supporting the Drosophila telomere elongation model by retrotransposition. The h igh incidence of terminal chromosome deficiencies occurring in natural Drosophila populations is discussed in view of the telomere structure at 2L.