Here Are All The Discoveries That Had To Happen Before Two Scientists Could Find DNA’s Structure

On this day in 1953, James Watson and Francis Crick (better known today by their surnames), finished building their model of DNA’s structure.

They went on to publish their findings in the April 25, 1953 edition of Nature to universal acclaim. But Watson and Crick weren’t working in a vacuum, as Howard Markel writes for Scientific American.

Just 50 miles away, he writes, scientists at King’s College, London were studying DNA as well, using X-ray crystallography. “One of them, Rosalind Franklin, succeeded in taking an X-ray diffraction pattern from a sample of DNA that showed a clearly recognizable cross or helical structure,” he writes. “Unbeknownst to Franklin, one of her colleagues let Watson see the image” a few days before Watson and Crick finished building their model.

That image told Watson and Crick that their theoretical model was on the right track. But, he writes, Franklin didn’t receive credit for her work until long after her death in 1958, four years before the others received a Nobel Prize along with Franklin's lab partner.

But Franklin wasn’t the only lesser-known person to contribute to the discovery of humanity's genes, writes Leslie Pray for Nature. Several generations of scientists had been working on the problem of DNA, and their research contributed to Watson and Crick’s discovery. According to Pray, this timeline of discoveries were essential for their work.

1869: Swiss chemist Friedrich Meischer discovers DNA, names it “nuclein”

Meischer discovered a substance inside white blood cells, which he named "nuclein." The name was later changed to "nucleic acid" and eventually "DNA," but that all came later.

Meischer’s discovery, which involved extracting white blood cells from pus-covered used bandages he got at a local hospital, wasn’t widely acknowledged by the scientific community for more than 50 years, she writes.

1919: Russian biochemist Phoebus Levene is the first to identify how DNA and RNA molecules are put together

Scientists did go on to work on understanding DNA, she writes, and in the 1910s Levene made a guess about how nucleic acids were structured that proved to be correct. He spent years breaking down and analyzing the nucleic acids in yeast, she writes. Based on that research, he proposed the idea that nucleic acids —  the now-familiar chains of DNA — were made up of a bunch of building blocks called nucleotides. The nucleotides themselves each contained one of four bases. He shared this research in 1919.

While it was initially the most accurate understanding of DNA’s structure, she writes, later advances revealed that Levene’s understanding was overly simplistic. However, it was a big step forward.

(1950) Erwin Chargaff writes the rules of DNA

Chargaff was one of few scientists to build on Levene’s work, Pray writes. He discovered two constants about DNA, one of which is still known as “Chargaff’s rule.” First, he discovered that DNA’s composition varies from one species to another, while Levene thought that all species had the same arrangement of nucleotides in their DNA. Second, he discovered relationships between the nucleotides which make up DNA that gave important clues to how it must be constructed. This last observation still bears his name.

Chargaff’s law and Franklin’s images, which were made with research partner Maurice Wilkins, lay the direct groundwork for Watson and Crick, she writes. “Using cardboard cutouts representing the individual chemical components of the four bases and other nucleotide subunits, Watson and Crick shifted molecules around on their desktops, as though putting together a puzzle,” she writes.

Eventually, through trial and error, they came up with the correct configuration. "It was simple; instantly you could explain this idea to anyone," Watson later reflected. But like most science, a lot of work and time went into that "eureka" moment.

Kat Eschner | | READ MORE

Kat Eschner is a freelance science and culture journalist based in Toronto.