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Mendel published his work on the heredity of peas in 1866 in which he noted that genes are passed from parent to offspring during reproduction.
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Griffith's Experiment In an experiment with lab mice, Frederick Griffith transfers the deadly component of a strain of pneumonia bacteria to an innocuous bacteria strain, and determines there must be a genetic "transforming factor" in the bacteria.
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Phoebus Levene discovers that the sugar deoxyribose is present in nucleic acids and later shows that DNA is made up of nucleotides, which are made up of a deoxyribose sugar, a phosphate group, and one of four bases.
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Oswald Avery, Colin MacLeod, and Maclyn McCarty show that DNA, and not protein, is the "transforming factor" Griffith first identified.
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Chargaff's rules Erwin Chargaff shows there are equal amounts of the nucleotides adenine (A) and thymine (T) as well as equal amounts of guanine (G) and cytosine (C), i.e. there is an A for every T and a G for every C.
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Alfred Hershey and Martha Chase show that viral DNA and not viral protein direct the replication of new viruses, confirming that DNA is the molecule that mediates heredity.
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Watson and Crick James Watson and Francis Crick describe the three-dimensional structure of DNA as a double helix: two spiraling strands held together by complimentary base pairs.
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Marshall Nirenberg, H. Gobind Khorana, Francis Crick, George Gamow, and other scientists crack the genetic code -- sixty-four nucleotide triplets that constitute a universal genetic code for all cells and viruses.
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Sanger Sequencing Animation Fred Sanger and others sequence DNA.
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PCR PCR, to date the most accurate and sensitive method for amplifying DNA, is developed by Kary Mullis.
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Human Genome Project Announcement of the final completion of the human genome sequence.
