FRACTIONATION OF DNA FROM EUKARYOTES BY PULSED FIELD GEL-ELECTROPHORESIS .1. DETECTION AND PROPERTIES OF DISCRETE DNA FRAGMENTS

The presence of discrete DNA fragments has been detected during the fr actionation of total nuclear DNA by agarose gel electrophoresis in an inverted electrical field. The set of fragments is monotypic for the v arious eukaryotes and consists of different fragments of chromosomal D NA unified in size. The capacity of the DNA fragments to be disrupted selectively by physical and chemical factors and also to reassociate u nder conditions leading to phage-lambda DNA oligomerization indicates that "sticky" ends may be present at the ends of the fragments which p romote the formation of multimeric structures. It is proposed that the set of discrete DNA fragments results from the specific degradation o f intact nuclear DNA and may reflect the different levels of the struc tural organization of the chromatin.