Probably one of the biggest milestones in the 20th century’s scientific findings, the discovery of the structure of DNA forever changed the biological research field. There is a widely known misconception that James Watson and Francis Crick discovered DNA in the 1950s, but that is not the case. The origins of the DNA molecule’s discovery dates back to 1871, when a Swiss physician and biologist, Friedrich Miescher, in collaboration with a german chemist, Albrecht Kossel, found phosphate-rich chemicals, nucleic acids, from the nuclei of white blood cells in Felix Hoppe-Seyler’s laboratory at the University of Tübingen in Germany.
This discovery paved the way for many breakthroughs in the identification of the components of the formerly called nucleine molecule. After Phoebus Levene (a Lithuanian-american physicist turned chemist) discovered ribose in 1909 and desoxyribose in 1929, he identified the components of DNA. He came to the conclusion in 1919 that the components were linked together in the order phosphate-sugar-base to form units, which he named nucleotide, and that the DNA molecule is actually a sequence of these nucleotide linked by the phosphate groups molecule. In 1910, he formulated a hypothesis stating that DNA is formed with the same amounts of adenine, guanine, cytosine, and thymine (the four types of nucleotides), later known as the tetranucleotide hypothesis. An Austro-Hungarian biochemist named Erwin Chargaff proved this theory wrong. He discovered two fundamental rules: the number of guanine units is the same as cytosine units and the number of adenine units equals the one of thymine units (total purines = total pyrimidines), and the base composition of DNA varies from one organism to another. This changed the dogma and made DNA a better hypothetical carrier of genetic material than protein. This dogma was instigated by a Russian biologist Nikolai Koltsov, whom in 1927 had the intuition that heredity was based on a “giant hereditary molecule” consisting of “two mirror-like strands reproducing in a semi-conservative manner using each strand as a model “and that the molecule is a protein one.
Avery, MacLeod and McCarty followed Frederick Griffith‘s work and conducted a series of experiment that led the way to uncover in 1943 the role of DNA as the vector of the genetic information.
Once it was set that DNA is the carrier of genetic information and its composition was known, the remaining intrigue was to know the structure of it. Rosalind Franklin, a British physicist and chemist, studied DNA fibers by X-ray diffraction. By precisely controlling the humidity of the samples, she managed to distinguish two forms of DNA (A and B), thus contradicting Maurice Wilkins and James Watson‘s hypothesis that stated that the phosphates were at the heart of the molecule. In May 1952, Raymond Gosling, Franklin’s PhD student, took an X-ray diffraction image of crystallized DNA famously known as photo 51. This was the most determining step towards assessing the structure of DNA. Maurice Wilkins, Franklin’s collaborator from Kings college in London, showed two scientists, British Francis Crick and American James Watson, the photo 51 without Franklin’s knowledge. In 1953, Crick and Watson, based on photo 51 and Chargaffs’ work, went on to suggest that DNA has a three-dimensional double-helical structure.
This shows that although Watson and Crick were the first to accurately describe the structure of DNA, their work is vastly a compilation of many incredible discoveries made by all of the scientists mentioned above, and they all deserve the recognition these two have solely gotten over the years.
Most people say that it is the intellect which makes a great scientist. They are wrong: it is character.
Albert Einstein
Biological culture 
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