The article by G. R. Wyatt, titled "The Purine and Pyrimidine Composition of Deoxypentose Nucleic Acids," discusses the accurate quantitative analysis of nucleic acids, particularly DNA and RNA. Early studies suggested that nucleic acids contained two purines and two pyrimidines in approximately equal proportions, leading to the tetranucleotide hypothesis. However, recent micro-analyses using methods like filter-paper chromatography and ultraviolet spectrophotometry have shown that this hypothesis is not consistent with the actual composition of nucleic acids. Wyatt describes the development of methods for separating and quantifying nucleic acid derivatives, including the use of paper chromatography and ultraviolet absorption techniques. He details the procedures for hydrolyzing DNA and RNA using formic acid and perchloric acid, and compares the results obtained from these methods. The study also examines the preparation of nucleic acids from various sources, such as ox spleen, herring testes, and calf thymus, and the impact of different treatments on their composition. The results of the analyses reveal significant differences in the molar ratios of purines and pyrimidines among different species, supporting the hypothesis that the composition of deoxyribonucleic acids varies between species but not within tissues of the same species. The presence of 5-methylcytosine is also identified as a characteristic difference between nucleic acids from different species. The article concludes by discussing the significance of the molar ratios of purines and pyrimidines and the presence of additional phosphate in nucleic acids, suggesting that the simple polynucleotide structure may be incomplete. The findings reinforce the idea that the composition of nucleic acids is crucial for their biological functions and specific activities, such as inducing mutations in bacteria.The article by G. R. Wyatt, titled "The Purine and Pyrimidine Composition of Deoxypentose Nucleic Acids," discusses the accurate quantitative analysis of nucleic acids, particularly DNA and RNA. Early studies suggested that nucleic acids contained two purines and two pyrimidines in approximately equal proportions, leading to the tetranucleotide hypothesis. However, recent micro-analyses using methods like filter-paper chromatography and ultraviolet spectrophotometry have shown that this hypothesis is not consistent with the actual composition of nucleic acids. Wyatt describes the development of methods for separating and quantifying nucleic acid derivatives, including the use of paper chromatography and ultraviolet absorption techniques. He details the procedures for hydrolyzing DNA and RNA using formic acid and perchloric acid, and compares the results obtained from these methods. The study also examines the preparation of nucleic acids from various sources, such as ox spleen, herring testes, and calf thymus, and the impact of different treatments on their composition. The results of the analyses reveal significant differences in the molar ratios of purines and pyrimidines among different species, supporting the hypothesis that the composition of deoxyribonucleic acids varies between species but not within tissues of the same species. The presence of 5-methylcytosine is also identified as a characteristic difference between nucleic acids from different species. The article concludes by discussing the significance of the molar ratios of purines and pyrimidines and the presence of additional phosphate in nucleic acids, suggesting that the simple polynucleotide structure may be incomplete. The findings reinforce the idea that the composition of nucleic acids is crucial for their biological functions and specific activities, such as inducing mutations in bacteria.