Phosphorus Compounds in Animal Tissues

The concept that nucleic acids are intimately associated with fundamental cellular processes has gained considerable favor within the last few years. This can undoubtedly be attributed to the researches of Caspersson and his associates. Caspersson, with the aid of ultraviolet spectrophotometry, has been able to measure the nucleic acids in various parts of the cell under a variety of experimental conditions. He has demonstrated, for example, that DNA ~ is found in certain portions of the chromosome and that its concentration undergoes cyclic changes, which can be correlated with mitosis (7). He has also been able to show that high concentrations of PNA * are found in the cytoplasm of cells actively engaged in protein synthesis, and in the cytoplasm of such rapidly growing tissues as embryos, and rnalignant tumors (6, 8-10). The peculiar localization of DNA in the chromosomes led to the hypothesis that it is closely associated with, if not in fact identical with, the genes. A barrier to this i&a has been the comparative simplicity of the structure of DNA in contrast to the wide variety of known genes. Nevertheless, the first direct experimental evidence in support of this hypothesis has now appeared. In a classical piece of work, Avery, MacLeod, and McCarty isolated a DNA from Pneumococcus Type III that was capable of inducing the transformation of Pneumococcus Type II into Type III (2). These are only a few of the findings that could be cited to show the importance of nucleic acids in cellular physiology, but as the subject has been adequately reviewed (12, 15, 19, 20, 27, 31, 36) it need not be further considered here. The need for quantitative chemical analyses of homologous normal and cancer