Abstract
With inhibitors of DNA synthesis used in the presence of ethidium bromide, it has been possible to distinguish between synthesis of informational DNA (I-DNA) and that of nuclear DNA. Hydroxyurea depresses I-DNA synthesis preferentially but does not affect DNA transport between cell compartments. 5-Fluorodeoxyuridine and cytosine arabinoside reduce synthesis of I-DNA to a much lesser degree than that of nuclear DNA.