Homologies between the contiguous and fragmented rRNAs of the two Plasmodium falciparum extrachromosomal DNAs are limited to core sequences.

Plasmodium falciparum contains two extrachromosomal DNAs, a 6 kb linear element and a 35 kb circular DNA; both encode rDNA sequences. The 6 kb element rDNAs comprise fragments of both large and small subunit rRNAs. Comparison of these with corresponding rDNA sequences from the 35 kb DNA and E. coli show that sequences conserved between the three are largely confined to highly conserved core regions; in fact, most of the 6 kb rDNA sequences correspond to core regions. Both the 6 kb element and 35 kb rDNAs show less conservation to each other than to E. coli sequences, suggesting that the two extrachromosomal DNAs of P. falciparum are not closely related. The characteristics of the fragmented rRNAs from the 6 kb element suggest they are functional, possibly in mitochondrial ribosomes.