ORGANELLE DNAS - THE BIT PLAYERS IN MALARIA PARASITE DNA-REPLICATION

The replication mechanics of the extrachromosomal DNAs of the malaria parasite are beginning to be unravelled. At 6 kb, the mitochondrial ge nome is the smallest known and, unlike higher eukaryotes, its multiple copies per cell occur as polydisperse linear concatemers. Here, Don W illiamson, Peter Preiser and Iain Wilson discuss recent evidence that this DNA replicates by a process akin to those of certain bacteriophag es, which make use of extensive recombination coupled with rolling cir cles. The parasite's second extra-chromosomal DNA, a 35 kb circular mo lecule thought to be a plastid remnant inherited from a remote photoau totroph, probably replicates in a move familiar fashion from conventio nal origins or D loops. Improved understanding of both organelle's rep licative mechanisms could give new leads to malaria chemotherapy.