INVERTED REPEAT STRUCTURE AND HOMOLOGOUS SEQUENCES IN THE LD(1) AMPLICONS OF LEISHMANIA SPP

In the parasitic trypanosomatids of the genus Leishmania, novel circul ar (CD) and linear (LD) multicopy genetic elements arise de novo eithe r spontaneously or as a result of drug selection. We report that the L D(1) minichromosomes of L. donovani, L. major and L. mexicana (ranging in size from 180 to 230 kb) have an inverted repeat structure and con tain homologous sequences located at similar distances from the telome re; one half of the chromosome being the mirror image of the other. Th ey must therefore have originated from a unique conserved source chrom osome; the size polymorphism being generated by the point at which inv ersion occurs. The circular CD1 elements appear to be circularised seg ments of the LD(1) elements. These observations lead to a unified conc ept of how minichromosomes LD(1) and circular CD1 genetic elements wit hin the Leishmania and contribute to evolution of karyotype.