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Gregor Mendel shows that the characteristics of pea plants are passed along in a predictable way. His discovery begins the science of genetics.

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Walter Sutton shows that chromosomes carry the cell's units of inheritance.

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Thomas Hunt Morgan demonstrates that genes are arranged in linear fashion on the chromosomes of the fruit fly.

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Frederick Griffith discovers that bacteria contain a molecule that can transfer genetic information from cell to cell.

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Oswald Avery, Colin Maclead, and Maclyn McCarty show the substance that Griffith discovered is DNA.

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Erwin Chargaff analyzes the base composition of DNA in cells. He discovers that the amounts of adenine and thymine are almost always equal, as are the amounts of guanine and cytosine.

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Alfred Hershey and Martha Chase confirm that the genetic material of viruses is DNA, not protein.
Rosalind Franklin records a critical X-ray diffraction pattern, demonstrating that DNA is in the form of a helix.

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Hershey and Chase's experiment concluded that little sulfur containing material entered the bacterial cell. However no specific conclusions can be made regarding whether material that is sulfur-free enters the bacterial cell after phage adsorption. Further research was necessary to conclude that it was solely bacteriophages' DNA that entered the cell and not a combination of protein and DNA where the protein did not contain any sulfur.

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James Watson and Francis Crick publish their model of the DNA double helix. The model was made possible by Franklin's work.

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discovery of dna double helix: watson and crick

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Discovery of DNA Double Helix: Watson and Crick | Learn Science at Scitable

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The landmark ideas of Watson and Crick relied heavily on the work of other scientists. What did the duo actually discover?

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Craig Venter and Francis Collins announce the draft DNA sequence of the human gename at a White House ceremony in Washington, D.C. The final version is published in 2003.