The chemical code of life was first found in pus
In short: In 1869, a Swiss biochemist isolated the substance that would eventually become the foundation of modern genetics. By treating white blood cells with acid, he revealed a precipitate that revealed the existence of nucleic acids—the molecules responsible for storing the instruction manual for every living thing.
The journey to understanding DNA began with Friedrich Miescher, who sought to determine the chemical composition of leucocytes. Using pus from fresh surgical bandages as his source, Miescher observed that treating the nucleus with acid produced a precipitate he named 'nuclein.' This discovery laid the groundwork for the identification of nucleic acids, which were later characterized by Richard Altmann and Albrecht Kossel as being composed of purine and pyrimidine bases, a sugar, and a phosphate group.
The architecture of these molecules is defined by their monomeric units: nucleotides. Each nucleotide consists of a 5-carbon sugar (deoxyribose in DNA), a nitrogenous base, and one or more phosphate groups. In the DNA polymer, these units link to form a backbone of alternating ribose and phosphate groups. The nitrogenous bases—adenine and guanine (purines) and cytosine and thymine (pyrimidines)—form the 'rungs' of the double helix. A key chemical detail is the N-glycosidic bond, which links the base to the 1' carbon of the sugar, while the phosphate group attaches to the 5' carbon.
The functional logic of DNA is governed by specific ratios and processes. In the 1930s, Erwin Chargaff discovered that in any given species, the amounts of cytosine and guanine are always equal, as are those of adenosine and thymine. For instance, the human genome maintains a balance of 20% C, 20% G, 30% A, and 30% T. This genetic information is not static; it is actively read by cells to produce RNA and proteins through transcription and translation, allowing for the replication and inheritance of life across generations.
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Sources
- Summary by Intellect · source: Introduction to nucleic acids and nucleotides | High school biology | Khan Academy
- Also: Understanding biochemistry: structure and function of nucleic acids - PMC
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