Distribution of Polypyrimidine · Polypurine Segments in DNA from Diverse Organisms

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Abstract
Polypyrimidine.cntdot.polypurine segments are regions of duplex DNA which contain a highly asymmetric distribution of pyrimidine and purine nucleotides. A polypyrimidine in single-stranded DNA can be detected by its ability to form a complex with poly(A, G) which will bind to hydroxyapatite. DNA from a variety of organisms [Escherichia coli, Saccharomyces cerevisiae, Drosophila virilis, D. melanogaster, mouse, human, Rhesus monkey, calf, dog, pig, rabbit, Chinese hamster, chick embryo, adenovirus type 2 and adenovirus type 5] was tested; most contained polypyrimidines. The shape of the curve relating DNA size to percentage bound to hydroxyapatite, suggests that polypyrimidine .cntdot.polypurine segments occur widely in DNA from higher organisms, at intervals of 6000-8000 base pairs throughout the majority of the genome. Lower levels occur in DNA from yeast and Drosophila.