Isolation of the Bromouracil-Substituted Light Strand of Mouse Satellite DNA

Abstract

Mouse L-cells were grown in medium containing bromodeoxyuridine and fluorodeoxyuridine, and the DNA from these cells was centrifuged to equilibrium in alkaline cesium chloride. The bulk of the bromouracil-substituted DNA had a buoyant density lying between 1.82 and 1.85 g/cc. About 4–5% of bromouracil-substituted DNA was observed as a distinct peak with a buoyant density of 1.79 g/cc. After this DNA was purified by recentrifuging, nucleotide analysis revealed an asymmetric composition in which the base-pairing rules for double-stranded DNA were not obeyed. Comparison of the nucleotide composition with published data indicated that the bromouracil-substituted light strand of mouse satellite DNA had been isolated.