Genetics Timeline

  • Gregor Mendel

    Gregor Mendel
    Experiment -
    1.Self pollinated purple plants and self pollinated white plants (P generation)
    2. cross pollinated the P generation (F1 generation; all purple)
    3. self pollinated the F1 generation (F2 generation; 75% purple, 25% white) Contribution - Law of Segregation and Law of Independent Assortment
  • William Bateson and Reginald Punnett

    William Bateson and Reginald Punnett
    Experiment - with pea plants -
    1. PpLl X PpLl
    2. predicted 9:3:3:1
    3. got 3:0:0:1 Contribution - Punnett Square, linked genes
  • Thomas Hunt Morgan

    Thomas Hunt Morgan
    Experiment with fruit flies -
    1. crossed GgLl X ggll
    2. got GgLl, ggll, Ggll, ggLl Contribution - crossing over, sex-linked traits, and the affect chromosomes have on a trait
  • Archibald Garrod

    Archibald Garrod
    Experiment - Studied Alkaptonuria in families and how it was inherited. He realized that it was an autosomal recessive pattern of inheritance, which led to his contributions Contributions - genes dictate phenotypes through enzymes
  • Frederick Griffith

    Frederick Griffith
    Experiment with Rats -
    1. injected "s" bacteria into a mouse; died
    2. "r" bacteria into a mouse; lived
    3. heat-killed "s" into mouse; lived
    4. heat-killed "s" and "r" bacteria into mouse; died Contribution - Transformation
  • George Beadle and Edward Tatum

    George Beadle and Edward Tatum
    Experiment - exposed bread mold to x-rays, which caused mutations. These mutations caused changes in enzymes. This led them to discover the one-gene, one-polypeptide theory Contributions - One gene - One polypeptide theory
  • Erwin Chargaff

    Erwin Chargaff
    Experiment - Chargaff collected DNA from organisms and seperated it using paper chromatography and it wa then analyzed. Contributions - Amount of Adenine = amount of thymine, amount of cytosine = amount of guanine, Adenine always pairs with Thymine, Cytosine always pairs
  • Rosalind Franklin and Maurice Wilkins

    Rosalind Franklin and Maurice Wilkins
    Experiment - took x-ray crystallographic phtographs of DNA Contributions - DNA is a helix
  • Alfred Hershey and Martha Chase

    Alfred Hershey and Martha Chase
    Experiment -
    1. Mixed radioactive phages with bacteria
    2. agitated the phages in a blender to seperate the phages outside the bacteria from the cells and their contents
    3. Centrifuged the mixture so bacteria form a pellet at the bottom of the test tube
    4. measured the radioactivity in the pellet and the liquid Contribution - Determined that DNA was the genetic material
  • James Watson and Francis Crick

    James Watson and Francis Crick
    Experiment -
    used photos from Rosalind Franklin and Maurice Wilkins' experiment and decided that the DNA had a double-helix formation Contributions - DNA was a double helix made of 2 polynucleotide strands; diameter = 2nm and nitrogen bases were .33 nm apart
  • Marshall Nirenberg

    Marshall Nirenberg
    Experiment - Produced RNA composed of only Uracil, then added it to a substance that contained DNA, RNA, and ribosomes. He then added DNase, which breaks down DNA. He added a radioactive amino acid and discovered the genetic code for phenylalanine is UUU. Contributions - codons and messenger RNA