DNA Structure: The Discovery of the Double Helix

DNA defines your biological makeup, creating all your unique physical quirks, from the colors of your eyes to the length of your legs. DNA is the blueprint of all living things, which makes keeping it in proper working order pretty important. DNA damage has been linked to cancer and other harmful diseases.
It’s amazing to think that, despite its importance to our very existence, DNA is a relatively recent discovery. Let’s take a look at how DNA and the familiar double helix structure were discovered.
Naming DNA
Back in 1868, Friedrich Miescher, a Swiss physician, isolated a compound he called nuclein that existed in the nuclei of all cells. Nuclein eventually became what we know as nucleic acid, part of DNA—deoxyribonucleic acid.
A couple years before Miescher discovered nuclein, a monk named Gregor Mendel conducted some very important research on peas. Not the most exciting of research specimens, but stick with me. See, Mendel discovered for the first time that certain traits in peas—shape, color, texture—were inherited based on what we know as genes.
Putting the Pieces Together
By the late 1940s, people knew and understood that DNA was the molecule responsible for creating life, even if it seemed too simple to be true. The science community was also well aware that DNA was composed of four nucleobases: adenine, thymine, cytosine, and guanine. However, the greatest mystery of DNA was its structure. Despite all the ideas—many reasonable, some highfalutin—no one had actually seen DNA up close.
Scientists had two basic theories about DNA. One stated that DNA molecules were shaped like a double helix. The other suggested that the DNA bases—pairs of adenine and thymine, cytosine and guanine—were on the inside of the molecule while the phosphate backbone was on the outside. The problem was linking those two things together.
Watson, Crick, Wilkins, and Franklin
James Watson and Francis Crick tested their theories about DNA structure using simple stick and ball models, but it was the work of Rosalind Franklin and Maurice Wilkins that eventually led to the discovery.
Franklin and Wilkins originally worked with X-ray crystallography. Shining X-rays on a crystal allowed the two to record the crystal patterns on a strip of film. Turns out, the same process could be used on certain biological molecules, including DNA.
It was through these means that Rosalind Franklin took the renowned “Photograph 51.” The photo shows a fuzzy X in the center of a molecule. That X indicated the double helix structure, changing the face of DNA research.
The photograph was shown to Watson and Crick in 1953, and the two presented the findings, earning Nobel Prizes in the process. Rosalind Franklin, whose data was what led to the discovery, wasn’t nominated for the Nobel Prize for her work. She died in 1958 from ovarian cancer, sealing her fate because only living persons could be nominated. Fortunately, Franklin wasn’t forgotten. Her life and her work are still honored and paved the way for modern genetics and research.
We are just bundles of DNA. It’s amazing to think what these microscopic things do for you. To learn more about DNA and genetics, visit your local public library.