The structure of DNA was unraveled in 1953, but it was actually first identified in 1868 in a small laboratory in Germany by a Swiss scientist named Friedrich Miescher.
When I inquire about the individual who discovered DNA, I typically receive one of two responses: “I don’t know” or “Watson and Crick”.
In most science textbooks at the school level, the names that appear during the introduction to DNA are James Watson, Francis Crick, and Maurice Wilkins. Their Nobel Prize, which was awarded in 1965, is emphasized alongside a famous image of Watson and Crick admiring their double-helix model. The Prize was given “for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material.” It is important to note the words “molecular structure,” not “discovery.” So, who actually discovered DNA?
Friedrich Miescher – The First to Identify DNA
Friedrich Miescher was born in Basel in 1844 (Photo Credit: public domain/Wikimedia Commons)
Friedrich Miescher was born into a family deeply involved in science on August 13, 1844 in Switzerland. Both his father and uncle, Johann F. Miescher and Wilhelm His, respectively, were esteemed physicians, anatomists, and professors at the University of Basel. Miescher displayed a strong interest in science and initially pursued the study of medicine in Basel, but later realized that research would better satisfy his curiosity about the natural world.
How Friedrich Miescher Identified DNA
The story of DNA begins in 1868 when Friedrich Miescher joined Felix Hoppe-Seyler’s laboratory. Miescher was intrigued by the chemical composition of cells.
Hoppe-Seyler’s laboratory was a place where biology and chemistry intersected. This environment provided Miescher with the necessary tools to investigate. Using pus from fresh surgical bandages obtained from a nearby clinic, Miescher extracted leukocytes, the cells he chose to work with.
Friedrich Miescher’s laboratory in Tübingen, Germany (Photo Credit: public domain/Wikimedia Commons)
Miescher was a meticulous scientist, meticulously documenting every detail and working with great caution. This careful approach allowed him to detect something peculiar among proteins and lipids. While conducting experiments, he observed that a substance precipitated under acidic conditions. Intrigued and excited, he decided to further explore this unusual precipitate.
He conducted several experiments to isolate the substance from the solution. This unknown precipitate dissolved when the solution was made alkaline, but reappeared when the solution was neutralized. Even when the solution was made acidic again, the substance did not dissolve back into the solution.
Chemical Experiments Conducted by Miescher to Confirm DNA
Proteins contain both positively and negatively charged molecules in their structure. Depending on the pH of the solution, the entire protein may carry a positive or negative charge, causing it to remain dissolved in the solution.
The interaction between the ions in the water and the charged species on the protein helps to keep the protein dissolved in the solution. However, when the protein reaches a specific pH (which is unique for each protein), its net charge becomes zero, meaning it is no longer charged. At this pH, the protein molecules start to interact with each other instead of with the surrounding ions. This interaction causes the proteins to come together and precipitate out of the solution. This pH is known as the isoelectric point or pI. By changing the pH away from its pI, the protein will dissolve back into the solution.
Miescher discovered that his precipitate did not dissolve when exposed to various acidic pH levels. Based on this observation, he concluded that the precipitate was not a protein.
To confirm his findings, Miescher conducted several additional tests. He burned the precipitate and found the typical organic elements such as oxygen, carbon, hydrogen, and nitrogen. However, he did not find sulfur, which is commonly found in most proteins. He also noted a significant amount of phosphorus in the precipitate, which is not present in other biomolecules.
Miescher also subjected the precipitate to proteases, enzymes that break down proteins into amino acids. The proteases had no effect on the precipitate, further supporting his belief that it was not a protein. Additionally, Miescher knew from previous research that the substance was found in the nucleus, so he named it nuclein.
Miescher published his discovery in 1871. He continued to study nuclein, using salmon sperm as the material. His work revealed that the unusual phosphorus in nuclein exists as phosphoric acid. He also deduced that nuclein must have a high molecular weight because it diffused poorly. He correctly guessed that a molecule called protamine was associated with nuclein.
These substances together made up the mass of the sperm heads that Miescher was studying. Subsequent research confirmed Miescher’s conclusions.
After Miescher, his research focus shifted, and he became burdened with other responsibilities as a professor. The study of DNA was taken up by other scientists.
Many chemists, including those who knew Miescher and Hoppe-Seyler, began studying nuclein. Albrecht Kossel, a researcher in Hoppe-Seyler’s lab who later won a Nobel Prize, discovered that nuclein consisted of four bases and sugars. Eduard Zacharias, a botanist, connected the concept of chromosomes with nuclein, demonstrating that nuclein was an important component of chromosomes.
Despite these findings, DNA received little attention from the scientific community at that time. Most experts, including Miescher, believed that proteins were the hereditary components rather than nucleic acids (later renamed by Richard Altmann). Many reasoned that nucleic acids were chemically too simple to account for the diversity of life. Proteins, on the other hand, consisted of 20 different amino acids and were considered complex enough to explain the variety of life forms.
The importance of nucleic acids was largely overlooked, leading to a decline in research on the molecule and a shift in focus towards proteins. However, a series of experiments conducted by Griffith, Avery, MacLeod, McCarthy, Hershey, and Chase proved that DNA was indeed the genetic material in cells. Despite this discovery, the structure of DNA still remained unknown, making it difficult to confirm its significance. Various scientists, including Watson, Crick, Wilkins, Rosalind Franklin, and Linus Pauling, were actively working to unravel the structure of DNA. Through a combination of luck, ingenuity, and inspiration, Watson and Crick were the first to successfully determine the structure of DNA, known as the double helix. This breakthrough revolutionized the field of nucleic acids, leading to a surge in research and groundbreaking discoveries over the next few decades. Friedrich Miescher, a key figure in the study of nucleic acids, left a lasting impact on the field, and his contributions continue to shape our understanding of evolution, health, and the origins of life on Earth.