Further studies and electron microscopic characterization of Plasmodium berghei DNA

The average length and the interspersion pattern of repetitive DNA sequences in the Plasmodium berghei genome have been studied by electron microscopy. Within the limitations posed by the relatively high genome complexity, analysis of partially renatured total DNA indicates that repetitive sequences do not occupy preferential positions along the genome, but are widely dispersed (one in approx. 8000 base pairs of unique DNA). Structures appearing as loops flanked by inverted repeats are present. Analysis of the repetitive fraction purified by hydroxyapatite chromatography shows that the average length of rapidly reassociating repetitive structures is around 800 base pairs with 90% of the length distribution between 400 and 1400 base pairs. Suitable extraction methods, preserving circularity of extrachromosomal DNA components, allow the detection of molecules which can be identified as mitochondrial DNA, 10.5 +/- 0.4 microns long.