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In 1869, Friedrich Miescher isolated "nuclein," DNA with associated proteins, from cell nuclei. He was the first to identify DNA as a distinct molecule. Phoebus Levene was an organic chemist in the early 1900's.
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1871-Lord Kelvin suggests that "the germs of life might have been brought to the Earth by some meteorite," an idea that will enjoy support a century later. 1873-Francis Galton publishes a paper entitled "Hereditary Improvement" arguing that people "of really good breed" should be encouraged to reproduce while their inferiors should be discouraged from doing so. This, he argues, will improve humanity the way selective breeding improves livestock.
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Griffith's experiment discovering the "transforming principle" in pneumococcus bacteria. Griffith's experiment, reported in 1928 by Frederick Griffith, was the first experiment suggesting that bacteria are capable of transferring genetic information through a process known as transformation.
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The major part of his career was spent at the Rockefeller University Hospital in New York City. Avery was one of the first molecular biologists and a pioneer in immunochemistry, but he is best known for the experiment ,published in 1944 with his co-workers Colin MacLeod and Maclyn McCarty, that isolated DNA as the material of which genes and chromosomes are made.
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The first rule was that in DNA the number of guanine units are merely equal to the number of cytosine units, and the number of adenine units are merely equal to the number of thymine units. This hinted at the base pair makeup of DNA. The second rule was that the relative amounts of guanine, cytosine, adenine and thymine bases varies from one species to another. This hinted that DNA rather than protein could be the genetic material.
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The Xray diffraction images produced by him and Rosalind Franklin, led to the deduction by James Watson an Francis Crick of the 3-dimensional helical nature of DNA. Wilkins shared the 1962 Nobel Prize in Physiology or Medicine with Watson and Crick. The DNA molecule is shaped like a twisted ladder.
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The Hershey–Chase experiments were a series of experiments conducted in 1952 by Alfred Hershey and Martha Chase that helped to confirm that DNA is genetic material.
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The discovery in 1953 of the double helix, the twisted-ladder structure of deoxyribonucleic acid (DNA), by James Watson and Francis Crick marked a milestone in the history of science and gave rise to modern molecular biology, which is largely concerned with understanding how genes control the chemical processes within cells.
