Reassociation kinetics of the DNA of human acute leukemia cells

Human DNA isolated from normal phytohaemagglutinin-stimulated human lymphocytes and from acute leukemia blast cells have been studied by renaturation techniques using hydroxyapatite binding and DNA hyperchromism. In the leukemic genome, the unique sequences account for 62% of the genome of leukemic DNA. Repetitive sequences may be subdivided into at least three fractions: (a) foldback sequences, which represent 5% of the genome; (b) sequences with high repetition frequency (3. 10(4) times on the average), which represent 12% of the genome; (c) sequences with low repetition frequency (10 times on the average), which represent 16% of the genome. The average length of the repetitive sequences is evaluated to be between 200 and 500 nucleotides. There are at least two patterns of interspersion of repetitive sequences with unique sequences of different length: short (about 2000 nucleotides on average) and long (not defined). The results of our experiments on DNA from normal phytohaemagglutinin-stimulated human lymphocytes are in close agreement with those reported by other authors studying different types of human cells. The human leukemic DNA, as far as the parameters that have been studied, does not significantly differ from normal human DNA.