Extensive homologies between Leishmania donovani chromosomes of markedly different size

The smallest chromosome (230 kb) of the HU3 stock of Leishmania donovani was purified from an orthogonal field alternation (OFAGE) gel, digested with PstI and cloned into the plasmid pUC13. When used to probe Southern blots of OFAGE gels, the cloned sequences recognised one or more large chromosomes in all L. donovani stocks and a small chromosome in HU3 and two additional L. donovani stocks (Khartoum and DD8). These probes recognised a single band on Southern blots of restricted genomic DNA regardless of their homologies to only large or large and small chromosomes. Analysis of lambda EMBL3 genomic clones selected with the same probes suggested that at least 30 kb of DNA was common to large and small chromosomes. Most of the cloned sequences were mapped to the same 50-kb SfiI fragment present in both chromosomes. These data indicate that two or more L. donovani chromosomes of markedly different size on OFAGE gels are extensively homologous.