title: Analysis of the breaking sites in the physical degradation of DNA.
abstract: The 3'-termini of procaryotic and eucaryotic DNA fragments obtained by shearing, sonication and irradiation have been analyzed. Analysis of the 3'-ends of DNA fragments was done by 32-P-labeling with terminal transferase, hydrolysis of products by spleen DNAase and spleen exonuclease and separation of labeled 3'-terminal nucleotides on polyethyleneimine plates. In the case of sonication the deviation from DNA base composition of 3'-terminal nucleotides is very close to random for Escherichia coli and Haemophilius influenzae DNA, whereas for calf thymus, mouse and yeast mitochondrial DNAs a significant increase in dA and decrease in dC was observed. Shearing at high salt released random 3'-termini in E. coli DNA and 3'-termini with 4 to 6% deviation from base composition in calf thymus DNA. In the case of gamma-irradiation no real differences have been found between E. coli and calf thymus DNA and 3'-terminal nucleotide composition is very close to random. Mechanical breakage of eucaryotic DNA seems to release 3'-termini having a composition which differs slightly but significantly from the average base composition of the DNA.
mesh_terms: D000818:Animals; D001483:Base Sequence; D002417:Cattle; D004247:DNA / Q000528:radiation effects; D004269:DNA, Bacterial; D004307:Dose-Response Relationship, Radiation; D004926:Escherichia coli / Q000032:analysis; D006193:Haemophilus influenzae / Q000032:analysis; D008099:Liver / Q000032:analysis; D008722:Methods; D051379:Mice; D008970:Molecular Weight; D009691:Nucleic Acid Denaturation; D009994:Osmolar Concentration; D011830:Radiation Effects; D012441:Saccharomyces cerevisiae / Q000032:analysis; D013010:Sonication; D013045:Species Specificity; D013950:Thymus Gland / Q000032:analysis
chemical_list: D004269:DNA, Bacterial; D004247:DNA