Before the Double Helix: Prehistory of DNA Research
A small exhibit entitled "Before the Double Helix: a Prehistory of DNA Research (1869-1953)" was displayed in the Moody Medical Library lobby during the Summer and Fall semesters of 2012. The timeline format of the exhibit recounted the history of DNA from its discovery to Watson and Crick's identification of the double helix structure.
DNA was discovered in 1869 by Friederich Miescher (1844-1895), a Swiss physician, while he was conducting research on the leukocytes found in pus in an effort to find a way to prevent wound infection during and after a surgical procedure. Miescher isolated a substance from the nucleus of pus cells that could not be identified as one of the known proteins; he called this new substance "nuclein" and published his findings in 1871.
Albrecht Kossel (1853-1927) continued research on the newly discovered nuclein and, between 1885 and 1901, made great progress in understanding the chemistry of "nucleic acids." Kossel believed that the true function of the nucleus was to be found in the formation of new tissue, and not as a kind of energy source for muscular contraction nor as a storehouse for phosphorus, two previously influential theories about nuclear function. Because of Kossel's findings, researchers were now able to study nucleic acid chemistry as a discipline.
Phoebus Levene (1869-1940) identified the structure of the nucleotide and found that ribose was the backbone sugar of RNA and deoxyribose in that of DNA. Levene's study implied that DNA was too simple to carry the information needed to transmit hereditary traits.
In 1923, Frederick Griffith (1879-1941) conducted an experiment using mice and the smooth and rough forms of several types of the bacteria pneumococcus. The experiments confused Griffith as, when combined, the type and/or form of the bacteria would change; it was widely believed that the types of bacteria were fixed. Griffith described this finding as a result of a "transforming substance."
Oswald Avery (1877-1955) expanded on Griffith's experiments by conducting his own "experiments by exclusion" and was able to determine that DNA was Griffith's "transforming substance." Impressed by Avery's work, Erwin Chargaff (1905-2000) decided to undertake a thorough chemical analysis of nucleic acids using the newly developed paper chromatography technique. In doing so, Chargaff effectively demolished Levene's tetranecleotide hypothesis. Chargaff also established three rules (Chargaff's Rules) which were vital to Watson and Crick's identification of the double helix structure in 1953.