Genetics dna

Genetics Timeline

  • Gregor Mendel

    Gregor Mendel
    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).
  • William Bateson and Reginald Punnett

    William Bateson and Reginald Punnett
    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.
  • Thomas Hunt Morgan

    Thomas Hunt Morgan
    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.
  • Archibald Garrod

    Archibald Garrod
    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.
  • Grederick Griffith

    Grederick Griffith
    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.
  • George Beadle and Edward Tatum

    George Beadle and Edward Tatum
    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.
  • Erwin Chargraff

    Erwin Chargraff
    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.
  • Alfred Hershey and Martha Chase

    Alfred Hershey and Martha Chase
    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.
  • Maurice Wilkins and Rosalind Franklin

    Maurice Wilkins and Rosalind Franklin
    Wilkins and Franklin took crystallograph pictures of DNA. Through these pictures, it was later determined that the shape of DNA was a double helix.
  • James Watson and Francis Crick

    James Watson and Francis Crick
    Watson and Crick studied Franklin's crystallograph picture of DNA and discovered DNA as having a double helix shape.
  • Marshall Nirenberg

    Marshall Nirenberg
    Nirenberg synthesized an RNA molecule by linking identical RNA nucleotides. Through this, he deciphered the first codon.