Abstract
Hydroxylamine (HA) inactivates T4 phages in two different ways. A non-mutagenio effect is strongest at an intermediate concentration of HA and a low concentration of salt, while high concentrations of both suppress this action. The second effect, observed only at high concentrations of HA and salt, is highly mutagenic. The mutagenic action of HA produces mottled T4 r plaques under conditions of little inactivation, while for longer treatment more and more pure r plaques have been observed. This has been examined quantitatively, r II-type mutations are distributed over the whole r II region and 94% of these can be induced to revert by 2-aminopurine. Certain nucleic acid bases treated with HA show a decrease in u.v. absorption while others gave no effect even when analysed by chromatography. The reacting bases are uracil, cytosine and 5-hydroxymethylcytosine; no reaction was found with purines, thymine, 5-methylcytosine and pseudouridine. The preferential action of HA with cytosine, of the DNA bases, suggests the direction of the mutagenic effect.
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