Incorporation of Halogenated Uracils

A variety of structural analogues of purines and pyrimidines are known to affect the growth of viruses, bacteria and other micro-organisms, plants and animals. Some of these may exert their action through being incorporated into nucleic acids in place of the natural purine or pyrimidine. Such examples are: 8-azaguanine, a structural analogue of guanine, which has been shown to replace guanine in the ribonucleic acid (RNA) of tobaccomosaic virus (Matthews, 1953), and is incorporated into the RNA of turnip-yellow-mosaic virus (Matthews, 1955), of several micro-organisms (Henrich, Dewey, Parks & Kidder, 1952; Lasnitzki, Matthews & Smith, 1954; Matthews & Smith, 1956), of both mouse tumour and normal tissues (Mitchell, Skipper & Bennett, 1950; Mandel, Carlo & Smith, 1954; Lasnitzki et al. 1954), and 2thiouracil which is incorporated into the nucleic acid of tobacco-mosaic virus (Jeener & Rosseels, 1953; Matthews, 1956).