A Brief history of DNA |
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To fully grasp and appreciate the knowledge that we possess today about DNA, we must take a step back and examine a few of the key scientists throughout history that made this information a reality.
Early Discovery - Freidrich Miescher
The earliest discovery of what would eventually be called DNA was by the Swiss biochemist, Freidrich Miescher. In 1869, over 140 years ago, Miescher discovered a substance in the nucleus of pus cells that was rich in phosphorus and nitrogen. Miescher dubbed this substance Nuclein. Prior to this point in history, it was thought that protein was the hereditary material that was passed on from parent cells to daughter cells.
Hammerling’s Discovery
In the 1930’s a biologist by the name of Joachim Hammerling, in an effort to answer the question, where is hereditary information located, performed experiments on Acetabularia. Acetabularia is a one-celled green algae that has a cap, stalk and foot which contains the nucleus. Through experimentally removing the cap or foot of the Acetabularia, Hammerling was able to hypothesize that the hereditable material was contained in the foot and more specifically the nucleus. This is because when the cap was removed the algae were able to regenerate a new cap. However, when the foot was removed a new one did not form. At this point, the actual chemical nature of DNA was still very unclear however these experiments were also able to prove that protein was in fact not the material responsible for heredity.
Hershey and chase
One more nail in the coffin for protein not being genetic material came in 1952 by Alfred Hershey and Martha Chase and their work with bacteriophages. Bacteriophages are microscopic viruses composed of DNA and a protein coat. Being a virus, bacteriophages infect host cells with their own DNA to commandeer the cells biological machinery to produce more viral DNA. Through experimentation, Hershey and Chase found that only the DNA and not protein entered the target cell to direct viral DNA replication.
Double helix discovered
In 1953 the final piece of the DNA structure puzzle was identified by James Watson and Francis Crick. They found that the DNA molecule was in the shape of a double helix. For this discovery, Watson and Crick were awarded the Nobel Prize in 1962. However, Watson and Crick’s discovery would not have been possible without the work done by Rosalind Franklin. It was Franklins work with x-ray diffraction that indicated the helical nature of DNA as she raced against fellow scientist Maurice Wilkins who was also using x-ray diffraction techniques. Despite her key contribution to this major discovery, Franklin was not awarded the Nobel Prize as she died at the age of 37 and the Nobel Prize cannot be give posthumously.