Characterization of two DNA populations of Giardia lamblia.

Total DNA was isolated from the parasitic protozoan Giardia lamblia and separated into two distinct populations of different densities by centrifugation through CsCl gradients containing Hoechst dye 33258. The two populations obtained were characterized by restriction enzyme analysis and nucleic acid hybridization. The less-dense population contains non-repetitive DNA and may encode mainly structural genes, such as those for alpha- and beta-tubulin. Digestion of the DNA with several restriction endonucleases showed that the denser band was composed of a 5.5 kb unit which contains the G. lamblia ribosomal RNA cistron in tandem repeated organization.