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1952: an X-ray diffraction image of DNA was taken by Raymond Gosling in May 1952, a student supervised by Rosalind Franklin. [30] 1953: DNA structure is resolved to be a double helix by James Watson, Francis Crick and Maurice Wilkins. [31] 1955: Alexander R. Todd determined the chemical makeup of nitrogenous bases.
In the 1940s and early 1950s, experiments pointed to DNA as the portion of chromosomes (and perhaps other nucleoproteins) that held genes. A focus on new model organisms such as viruses and bacteria, along with the discovery of the double helical structure of DNA in 1953, marked the transition to the era of molecular genetics.
The timeline begins at the Bronze Age, as it is difficult to give even estimates for the timing of events prior to this, such as of the discovery of counting, natural numbers and arithmetic. To avoid overlap with timeline of historic inventions , the timeline does not list examples of documentation for manufactured substances and devices unless ...
1869 – Friedrich Miescher identifies DNA in the sperm of a trout. 1871 – Felix Hoppe-Seyler discovers invertase, which is still used for making artificial sweeteners. 1877 – Robert Koch develops a technique for staining bacteria for identification. 1878 – Walther Flemming discovers chromatin leading to the discovery of chromosomes.
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In April 2023, scientists, based on new evidence, concluded that Rosalind Franklin was a contributor and "equal player" in the discovery process of DNA, rather than otherwise, as may have been presented subsequently after the time of the discovery. [7] [8] [9]
Some 20 years ago, David Reed, a coauthor of the new study and a researcher and curator at the Florida Museum of Natural History, found that human head lice are composed of two ancient lineages ...
1952 – Alfred Hershey and Martha Chase showed that DNA is the genetic material in bacteriophage viruses. 1952 – Rosalind Franklin concluded that DNA is a double helix with a diameter of 2 nm and the sugar-phosphate backbones on the outside of the helix, based on x ray diffraction studies. She suspected the two sugar-phosphate backbones have ...