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Mendel cross fertilized pea plants to determine the parentage of the plants. He started with true breeding plants. Through his experiments, he discovered the fundamental principle of genetics, that parents pass on their traits to their children. He also discovered dominance and recesseive traits, and created Mendel's Laws of Inheritance (law of segregation and the law of independent assortment).
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Bateson and Punnett crossed doubly heterozygous sweet peas, expecting a 9:3:3:1 raio, but instead discovered linked genes. Punnett also originated Punnett squares.
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Morgan crossed fruit flies using a test cross. He crossed a white-eyed male fruit fly witha red-eyed female, and discovered that all the offspring had red eyes. When he breeded those flies, however, some had white eyes, but only the males. Through this he discovered sex-linkage, and in turn discovered crossing over and recombination.
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Garrod hypothesized that disease reflects an inabiity to make a particular enzyme. Through this hypothesis he showed that it was indeed a lack of enzyme that caused some diseases.
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Griffith tested pneumonia bacteria on mice. He used one lethal, one harmless, with the results being obvious. He then, however, heated the lethal pneumonia, which killed it making it armless. He finally mixed the harmless with the heated bacteria, making a lethal substance that killed the mice. Through this experiment, he discovered transformation.
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Beadle and Tatum observed orange bread mold and its inability to grow from a lack of a specific enzyme. Through this observations, they created the one gene-one enzyme hypothesis, concluding that the function of an individual gene is to dictate the production of a specific enzyme.
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Erwin Chargraff discovered that the amount of edenine was equal to the amount of thymine, and the amount of guanine is equal to the amount of cytosine, in DNA. He showed this using paper chromatography and an ultraviolet spectrophotometer.
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Hershey and Chase used radioactive DNA and protein, with a bacteriopage, to deduce that DNA, not protein, was the hereditary material. By adding the bacteriophage and blending, Chase and Hershey saw that it was the DNA which entered the host cell, not the protein.
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Wilkins and Franklin took crystallograph pictures of DNA. Through these pictures, it was later determined that the shape of DNA was a double helix.
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Watson and Crick studied Franklin's crystallograph picture of DNA and discovered DNA as having a double helix shape.
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Nirenberg synthesized an RNA molecule by linking identical RNA nucleotides. Through this, he deciphered the first codon.
