DROSOPHILA TELOMERES - NEW VIEWS ON CHROMOSOME EVOLUTION

In Drosophila, chromosome ends (telomeres) are composed of telomere-sp ecific transposable elements (the retroposons HeT-A and TART). These e lements are a bona fide part of the cellular machinery yet have many o f the hallmarks of retrotransposable elements and retroviruses, raisin g the possibility that parasitic transposable elements and viruses mig ht have evolved from mechanisms that the cell uses to maintain its chr omosomes. It is striking that Drosophila, the model organism for many discoveries in genetics, development and molecular biology (including the classical concept of telomeres), should prove to have chromosome e nds different from the generally accepted model. Studies of these telo mere-specific retrotransposable elements raise questions about convent ional wisdom concerning not only telomeres, but also transposable elem ents and heterochromatin.