When was dna proven

Created by Rosalind Franklin using a technique called X-ray crystallography, it revealed the helical shape of the DNA molecule. Watson and Crick realized that DNA was made up of two chains of nucleotide pairs that encode the genetic information for all living things. Photo of x-ray crystallography Exposure 51 courtesy of King's College Archives.

King's College London. Click for larger image. The Discovery of DNA's Structure: They were hardly modest, these two brash young scientists who in declared to patrons of the Eagle Pub in Cambridge, England, that they had "found the secret of life.

The stunning find made possible the era of "new biology" that led to the biotechnology industry and, most recently, the deciphering of the human genetic blueprint. Watson and Crick's discovery didn't come out of the blue. While studying white blood cells, Miescher isolated a previously unknown type of molecule that was slightly acidic and contained a high percentage of phosphorus.

Miescher named this molecule "nuclein," which was later changed to "nucleic acid" and eventually to "deoxyribonucleic acid," or DNA.

Interestingly, Miescher did not believe that nuclein was the carrier of hereditary information, because he thought it lacked the variability necessary to account for the incredible diversity among organisms. Rather, like most scientists of his time, Miescher believed that proteins were responsible for heredity, because they existed in such a wide variety of forms. For multiple decades following Miescher's discovery, most scientists continued to believe that protein, not DNA, was the carrier of hereditary information.

This changed in , when biologist Oswald Avery performed a series of groundbreaking experiments with the bacteria that cause pneumonia. At the time, scientists knew that some types of these bacteria called "S type" had an outer layer called a capsule, but other types called "R type" did not.

Through a series of experiments, Avery and his colleagues found that only DNA could change R type bacteria into S type. This meant that something about DNA allowed it to carry instructions from one cell to another. This was not true of any other substances within the bacteria, including protein.

This result highlighted DNA as the "transforming factor," thereby making it the best candidate for the hereditary material. Under normal circumstances, a bacterial cell will reproduce by a form of cell division called binary fission.

When Avery, MacLeod, McCarty, Hershey, and Chase performed their experiments, scientists knew that binary fission involved the copying of the hereditary substance and the redistribution of this substance into two new cells.

So, when DNA was proven to be the material responsible for controlling the operations inside a single cell, it became easier to understand how the process of cell division and the transfer of the DNA could control the characteristics of newly born cells.

Therefore, although they did not state it explicitly, Hershey and Chase had presented experiments that clearly suggested that DNA controls the production of more DNA, and that DNA itself was the substance that directed the construction and function of living things. This discovery enabled investigators to put together the story of how DNA carries hereditary information from cell to cell.

Indeed, the experiments connecting heredity and the structure of DNA were happening in parallel, so the next few years would be an exciting time for the discovery of DNA function.

This page appears in the following eBook. Aa Aa Aa. The chemical nature and structure of DNA were not elucidated until the middle of the twentieth century.

Prior to that point, scientists had spent years speculating about which of the many types of molecules within cells contained the hereditary information. Was it protein? Was it something else — perhaps even a molecule they had yet to discover? Eventually, researchers zeroed in on DNA as the substance responsible for the transfer of traits from one generation to the next. Avery and McCarty concluded that the transforming substance, which produced permanent, heritable change in an organism, was DNA.

Although the paper describing their extraordinary findings was not submitted until December of , and published in the spring of , Avery, McCarty, and MacLeod had accumulated all the basic experimental information and presented it to the Rockefeller Institute's Board of Scientific Directors by early April Avery anticipated significant skepticism of their claim of genetic specificity for DNA, and was weary of a repeat of the turmoil caused by his work with Alphonse Dochez on antiblastic immunity several decades earlier.

Therefore he submitted the manuscript to several months of review and scrutiny by associates at the Hospital. What is more, despite Avery's confidence in their purification technique, he included in the final paper several cautionary statements that acknowledged the possibility that "the biological activity of the substance described is not an inherent property of the nucleic acid, but is due to minute amounts of some other substance absorbed to it or so intimately associated with it as to escape detection.

Avery's brother Roy was one of the first persons outside of the Hospital to be informed of their findings. In May , Avery wrote his brother to inform him that he would need to delay his retirement and provide an update on the exciting developments of the previous two years of research.

Avery noted that he and McCarty seemed to have identified the transforming substance: "In short, this substance is highly reactive and on elementary analysis conforms very closely to the theoretical values of pure desoxyribose nucleic acid.

Who could have guessed it? It touches genetics, enzyme chemistry, cell metabolism and carbohydrate synthesis. Although their findings were clearly revolutionary, their conclusions in this paper were cautious, and they presented several interpretations of their results.