Dna strands concept illustration

DNA timeline

By adria_16
  • Discovery of Nucleic Acids

    Discovery of Nucleic Acids

    Scientists found nucleic acids. Phoebus Levene later described DNA’s parts (sugar, phosphate, bases) and named the nucleotide, but guessed the wrong structure.
  • Griffith’s Transformation

    Griffith’s Transformation

    Frederick Griffith showed that something from dead harmful bacteria could change harmless bacteria. He called it “transformation.”
  • DNA Identified as Genetic Material

    DNA Identified as Genetic Material

    Oswald Avery, Colin MacLeod, and Maclyn McCarty proved that DNA, not proteins, caused transformation in bacteria.
  • Chargaff’s Rules

    Chargaff’s Rules

    Erwin Chargaff measured DNA bases and saw that adenine equals thymine, and cytosine equals guanine.
  • Hershey–Chase Experiment

    Hershey–Chase Experiment

    Alfred Hershey and Martha Chase used viruses with radioactive labels. They showed DNA, not protein, carries genes.
  • Building the DNA Model

    Building the DNA Model

    Watson and Crick first made a wrong model. Rosalind Franklin’s clear X-ray photo (Photo 51) revealed a double helix. Wilkins shared it, helping Watson and Crick design the correct shape.
  • Double Helix Published

    Double Helix Published

    Nature printed three papers: Watson Crick’s model, Wilkins’ work, and Franklin Gosling’s data. Franklin’s role was vital, but she was not credited properly.