DNA Timeline

By calvin.chapman2019

  • Franklin

    Franklin
    Franklin used x-ray diffraction to provide information on the structure of DNA fibers. She used x-ray machines to look at clear images of DNA to help her make her discoveries. Franklin introduced the use of x-ray diffraction to view the structure of DNA, which until then had not been used.

  • Chargaff

    Chargaff
    Chargaff discovered DNA "base ratios", also known as Chargaff's Rules. He stated in his rules that the amount of puridines are about the same or equal, and the amount of pyrimidines are about the same or equal. Chargaff studied different species and conducted careful experimentation. Also, he read the famous paper written by Oswald Avery and his colleagues. Before this, humans did not know that purines and pyrimidines are similar or equal in amounts.

  • Hershey and Chase

    Hershey and Chase
    Hershey and Chase confirmed that DNA was genetic material. They injected chemical tracers that resembled proteins and DNA into a type of rapidly reproducing virus called T2. They found that the tracers that resembled DNA were much more likely to be found in future generations of the cells. Until this point, scientists did not know that DNA was genetic material.

  • Watson and Crick

    Watson and Crick
    Watson and Crick discovered the double helix shape of DNA. They used cardboard cut outs to represent the nucleic acids and put the pieces together like a puzzle. They followed Chargaff's Rule to make this discovery. Until this point, Humans did not know that DNA existed in a double helix shape.

  • Meselson and Stahl

    Meselson and Stahl
    Meselson and Stahl supported that DNA replication was semi-conservative. They labeled the DNA of bacteria across generations using isotopes of Nitrogen. The patterns proved that DNA is replicated semi-conservatively. With this discovery, scientists now know for sure that DNA is replicated semi-conservatively.

  • Miescher

    Miescher
    Miescher discovered the structure called DNA. He filtered leukocytes off of old bandages and discovered a new substance inside the cells nuclei with chemical properties unlike any other protein, which ended up being DNA. Until then, scientists did not know what exactly DNA was.