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Miescher was the first to conclude that DNA is it’s own molecule. He came to this by isolating "nuclein," DNA with associated proteins, from a cell nucleus. This picture shows a vial of salmon sperm he used in separating the nuclein.
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Griffith used mice to experiment. He discovered that hereditary information passes between two strains of bacteria (R and S). R did not have an affect on the mice, but S was deadly. It was interesting that R would not have an effect by itself, but when mixed with heat treated S cells it was deadly.
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They decided to call Griffiths discovery the “transforming principle.” They investigated the different components of S and R and discovered that the nucleic acid was the deciding factor. Meaning that DNA controlled hereditary rather than protein which was assumed before this. The picture is a graph of studies used for the discovery.
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Erwin Chargraff iscovered the number of thymine and adenine is identical to the amount of cytosine and guanine for all DNA molecules.(A=T and G=C). He also concluded that different species DNA differ in proportions of adenine and guanine.
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They proved that DNA, not protein, shows expected properties of a hereditary molecule. “It transmits a full complement of hereditary information.” Hershey and Chase worked with bacteriophage, a bacterial virus. The pair completed experiments proving that the material a bacteriophage injects into bacteria is DNA, not protein. The diagram shows how they used the virus in their discovery.
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Pauling discovered that proteins were constructed of spiral structures. This was then later used in biology. Proposed that DNA was structured with three helices and bases located on the outside. based discoveries on other scientists' x-ray images. The image depicted what Pauling believed DNA structure looked like.
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Rosalind Franklin used x-ray crystallography to investigate DNA’s structure. Picture showed that DNA has 2 strands of nucleotides running in opposite directions and coiled into a double helix. Her and her partner proved this to be the structure of DNA.
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They took Franklin's discovery and used it for themselves. Created a model of DNA based off of Franklin's picture. Showed that bases were located on the inside of the double helix.
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Sanger obtained a protein sequence. This proved that proteins were ordered molecules, which lead him to the conclusion that DNA also have a sequence The picture shows sequences.
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The pair revealed that DNA is replication is semi-permeable. The double helix separates to form two single strands of nucleotides, then a new strand forms around the former.
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“father of genetic engineering”
Berg succeeded in inserting DNA bacteria into a virus’ DNA. He was the first to create a DNA molecule made of parts from multiple organisms. This led to a path for hybrid DNA. -
McClintock discovered “jumping genes”. Concluded that some genes could be “mobile”. She uncovered this while studying chromosomes in corn; a chromosome-breaking lotus that could change its position within a chromosome. She completed her work in the 40s and 50s, but was recognized in 1983.
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Kary Mullis created a process known as polymerase chain reaction(PCR), which means a small amount of DNA can be copied in large quantities over a short period of time.
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J. Craig Venter developed “expressed sequence tags”, (relatively short DNA sequences) which was a new strategy for the discovery and tagging of genes the revolutionized biological sequence.
