Molecular cloning and characterization of the ribosomal RNA genes of the cestode Echinococcus granulosus

1. The analysis of total protoscolex DNA and some rDNA recombinants of Echinococcus granulosus by restriction endonuclease mapping and hybridization to rDNA probes indicated the complex organization of the ribosomal RNA genes and that some repeat units are larger than 15 kb. The non-transcribed spacer can be up to 13 kb in length in some repeat units. 2. Restriction site polymorphism was detected mainly in the nontranscribed spacer regions although some polymorphism was also observed in the 28S rRNA coding region. 3. On the basis of Southern blot hybridization using EcoRI-digested genomic DNA, we conclude that the repeat units containing an extra EcoRI site are present almost in the same proportion as the repeat units without the extra EcoRI site in the 28S rRNA coding region.