DNA History

  • 1865 - The pea plant

    1865 - The pea plant
    In 1865, Gregor Mendel laid the foundation for genetics by unraveling the basic principles of heredity, although his work would not be recognized as "revolutionary" until after his death. In studying the common pea plant, Mendel demonstrated the inheritance of "discrete units" and introduced the idea that the inheritance of these units from generation to generation follows particular patterns. These patterns are now known as the "Laws of Mendelian inheritance."
  • 1869 - Isolated "nuclein"

    1869 - Isolated "nuclein"
    Friedrich Miescher, a Swiss researcher, noticed a sudden, unknown change in his work with white blood cells. By isolating the material, he found that it resisted protein-digesting enzymes. Further work led him to the discovery that the substance contained carbon, hydrogen, nitrogen, and large amounts of phosphorus without sulfur. Because he isolated the material from the nuclei of cells, he named the substance "nuclein." Today we know "nuclein" as DNA, a nucleic acid.
  • 1878 - Chromosomes during mitosis

    1878 - Chromosomes during mitosis
    In the late 19th century, microscope technology was relatively underdeveloped, leading to poor resolution of specimens. With patience and precision, Walther Flemming studied the threadlike material in the nucleus of cells at various times as cells divided. He named this threadlike material "chromatin" and successfully solved the process of mitosis and the arrangement of chromosomes at various points during the various stages of mitosis.
  • 1910-1912 - Genes linked to chromosomes

    1910-1912 - Genes linked to chromosomes
    In his "fly room" Thomas Hunt Morgan took on the challenge of determining how species change over time. Morgan understood the value of the common fruit fly as a model organism due to the rapidity of reproduction and the lack of expense in rearing large numbers of individuals. After studying thousands upon thousands of fruit flies, Morgan confirmed that genes are linearly arranged on chromosomes and that some genes are "linked," meaning that some genes tend to be inherited.
  • 1928 - Transformation

    1928 - Transformation
    Frederick Griffith developed the phenomenon called "transformation". Griffith studied two Streptococcus pneumoniae strains that differ in virulence, physical appearance, and capsular structure: the non-virulent R strain and the virulent S strain. An important key in an experiment in their research was mice dying when they were injected with a mixture of heat-killed S bacteria and live R bacteria.He observed that the bacteria had smooth capsules that were characteristic of the S strain.
  • 1938 - First images of DNA

    1938 - First images of DNA
    The first X-ray diffraction images of DNA were published in 1938 by William Astbury and his graduate assistant, Florence Bell. Astbury concluded that the bases lay flat, were stacked on top of each other like "penny piles", and were 3.4 spaced apart.
  • 1944 - DNA- The transforming agent

    1944 - DNA- The transforming agent
    Frederick Griffith; Oswald Avery, Maclyn McCarty y Colin MacLeod publicaron un artículo anunciando que el ADN era efectivamente el "agente transformador". La prueba definitiva fue cuando Avery y sus colegas pudieron mostrar que esa actividad transformadora no fue destruida por enzimas que degradan proteínas o ARN. Concluyeron que, "la transformación descrita representa un cambio químicamente inducido y específicamente dirigido por un compuesto químico conocido.
  • 1952 - DNA is the genetic material

    1952 - DNA is the genetic material
    Through their experiments with bacteriophages, Martha Chase and
    Alfred Hershey showed that DNA, not proteins, was the genetic material. Using radioactive phosphorus and sulfur, his famous blender experiment showed that bacteriophage DNA enters infected bacterial cells and not bacteriophage proteins.
  • 1952 - "Photo 51"

    1952 - "Photo 51"
    In 1951, Rosalind Franklin began taking X-ray diffraction photos of
    DNA in Maurice Wilkin's lab at Kings College in London. A talented crystallographer, Franklin trained at Cambridge and her photographs
    clearly showed that DNA was a double helix. Before posting
    her results and unknown to her, Wilkins showed the now famous
    "Photo 51" to James Watson. This particular image along with other data from the scientists was the inspiration for Watson and Crick for their DNA model.
  • 1953 - Nitrogenous structure bases

    1953 - Nitrogenous structure bases
    Jerry Donohue is the only person Watson and Crick thank in their role on the double helix. Being a specialist in crystal structures and Analysis, which also shared an office with Watson and Crick in Cambridge, pointed out that they were using the wrong structures for nitrogen bases, and that the correct structures would form hydrogen bonds with each other. This was a vital contribution to their final model so that in a few days they would build their famous structure.
  • 1953 - The Double Helix

    1953 - The Double Helix
    First DNA model: three strands wound around each other in a helix with phosphates in the nucleus. Next, they drew a second unsuccessful attempt at matching models as bases to similar bases. In April 1953, they published their famous double helix model for the structure of DNA. In that paper, Watson and Crick observed: "It has not escaped our knowledge that the specific pairing that we have immediately postulated suggests a possible copying mechanism for the genetic material.