Genetics Timeline

  • Gregor Mendel

    Gregor Mendel
    Experiment: using pea plants he prevented self fertilization by cutting of the stamens from purple flowers. He then transferred pollen form the stamen of the white flower to the purple flower. the offspring were all purple. he then self pollinated the new generation and their offspring were 3/4 purple.
    Contribution: discovered the fundamental principles of genetics. consisting of 2 genes from each parent, alleles seperate during meiosis, and one allele fully expressed, the other had no effect
  • William Bateson and Reginald Punnet

    William Bateson and Reginald Punnet
    Crossed two Heterozygous plants that exhibit dominant traits. The results did not match the predicted 9:3:3:1 ratio of a dihbrid cross. which led to their discovery of linked genes.
    Created the Punnet square and discovered linked genes.
  • Thomas Hunt Morgan

    Thomas Hunt Morgan
    He used Fruit Flys and he bred white eyes with red eyes. By doing that he figured out that white eyes was only with males so that meant that the eye color gene was on the sex chromosome.
    Dicovered crossing over and figured out how to map genes by using recombination frequency.
  • Archibald Garrod

    Archibald Garrod
    He observed that people with alkaptonuria congenital disorder, when exposed to air, their urine turns dark.

    His experiment suggests that genes dictate phenotypes through enzymes.
  • Frederick Griffith

    Frederick Griffith
    He used mice by giving them a harmless bacteria and a lethal bacteria to see if the mice would die. He mixed the lethal with the harmless and found that some died.

    This experiment led to the discovery that DNA controls the cells.
  • George Beadle and Edward Tatum

    George Beadle and Edward Tatum
    Experiment: Called the Orange Bread Mold experiment. They studied strains of the mold that were unable to grow on the usual simple growth medium. Each mutant turned out to lack an enzyme in a metabolic pathway that produced some molecule the mold needed. It also showed that each mutant was defective in a single gene.

    Contribution: This led to the one-gene-one enzyme hypothesis. which stated that the function of an individual gene is to dictate the production of a specific enzyme.
  • Erwin Chargaff

    Erwin Chargaff
    He noticed a pattern in the DNA model so he took samples of different DNA cells to find out that A=T and C=G.
    He gave us Chargraff's Rules. Which consists of that the amount of adenine in DNA was equal to the amount of thymine, and that the amount of guanine was equal to that of cytosine. A=T and G=C
  • Alfred Hershey and Martha Chase

    Alfred Hershey and Martha Chase
    Experiment: They injected radioactive protein into bacteria, then tested for radio activity. THen they saw that the radio activity was in the liquid not in the pellet. They did the same thing but with radioactive DNA, and found that radioactvity was in the pellet, not the liquid.
    Contribution: They demonstrated that DNA is the genetic material
  • Maurice Wilkins and Rosalind Franklin

    Maurice Wilkins and Rosalind Franklin
    They took an x-ray crystallo-graphic photo of DNA and that showed that DNA was a Helix.
  • James Watson and Francis Crick

    James Watson and Francis Crick
    Studies protein structure with x-ray crystallography. They noticed that the helix had a diameter of 2 nm. so they tried to construct a double helix using wire models of the nucleotides.
    Contribution: Deternined that DNA was a double Helix made of 2 plynucleotide strands
  • Marshal Nirenberg

    Marshal Nirenberg
    Synthesized the amino acid Phenylanine using the RNA codon UUU.
    He "broke the genetics code" and described how it operates in protein synthesis.