The Effects of g-Irradiation and of Aminopterin on the Metabolism of Formate-C 4 , Glycine-2-C 14 , and Adenine-8-C 14 by Chick Embryos

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Abstract
Irradiation of 60-hour chick embryos with CO60 gamma-rays in vitro reduced the uptake of formate-C14 and glycine 2-C14 into the guanine and thyamine of deoxyribonucleic acid (DNA) only with doses exceeding 1000 r. Lower doses had no effect. With adenine-8-C14 no effect was found with a radiation dosage as high as 20,000 r. All substrates were added immediately after irradiation followed by a 2-hour incubation period before fractionation of the embryos. Exposure of the embryos to aminopterin reduced formate-C14 uptake sharply into DNA, RNA, protein and acid soluble fractions but had no consistent effect on glycine-2-Cl4 or adenine-8-C14 uptake.