It is no coincidence that this article is published on April 25th. Today is International DNA Day, and so, today we are going to talk about the most important person in the history of DNA. I give you: Rosalind Franklin.

Does the name ring a bell? Probably not as much as it should. And that, precisely, is the scandal. Because while the names of Watson, Crick, and Wilkins resonate in every textbook and flaunt a Nobel Prize, the name of the woman who made their discovery possible was silenced, disregarded, and buried, literally and figuratively, before the world could recognize her genius.

Rosalind Franklin did not "collaborate" in the discovery of the double helix: she made it possible. Her famous Photograph 51, an X-ray diffraction image of breathtaking clarity, was the definitive proof that unveiled the structure of DNA. But that photograph left her lab without her permission, passed through the hands of a male colleague, and landed on the desk of those who are now listed as "the fathers of DNA." She, meanwhile, was not even informed. Nor cited. Nor invited to the Nobel banquet, which she wouldn't have been able to attend anyway: she died of cancer at 37, possibly due to radiation exposure from the experiments that would change biology forever.

This is the story of how science, that discipline that prides itself on objectivity, has also managed to be profoundly unfair. The story of a brilliant woman whose credit was stolen in life and dignity after death. Today, on DNA Day, we give her back the microphone.

Her Early Years

Rosalind Elsie Franklin was born on July 25, 1920, in Notting Hill, London, into an affluent, cultured Jewish family deeply committed to education and social justice. From a very young age, she stood out for an intelligence uncomfortable for the time: at six, her aunt wrote that she was "alarmingly clever," spent her time doing arithmetic for pleasure, and demanded to know the why of everything. In a society that expected girls to learn manners and little else, Rosalind had already decided at 15 that she would be a scientist.

Her father, however, did not approve. He believed that university was "no place for a woman" and tried to steer her towards social work. She stood firm and, thanks to the support of her mother and aunt, entered Newnham College, Cambridge, in 1938, one of the few institutions that admitted women, although they did not even grant them official degrees on equal terms with their male counterparts. There she studied Natural Sciences, specializing in physical chemistry, the branch that studies thermodynamics, spectroscopy, crystallography... while Europe bled during World War II.

After graduating in 1941, instead of taking refuge in a quiet laboratory, Rosalind rolled up her sleeves and dedicated herself to the war effort. Between 1942 and 1946, she worked at the British Coal Utilisation Research Association, where she researched the microstructure of coal and graphite. Her work, far from being an anecdote, was key to the development of better gas masks and, later, to laying the theoretical foundations of carbon fiber technology, which decades later would enable the development of carbon fibers and other advanced materials used today in airplanes, electric cars, medical prostheses, and even graphene. That study also earned her a Ph.D. from Cambridge in 1945, at just 25 years old.

Her real professional breakthrough came in Paris. Between 1947 and 1950, at the Laboratoire Central des Services Chimiques de l’État, Rosalind learned and perfected the technique that would change her life and the history of biology: X-ray crystallography. There, surrounded by colleagues who, for the first time, treated her as an equal, she became a world authority on the subject. When she returned to London in 1951 to join King’s College, she was already an elite scientist, with a unique technique for her time.

What she did not suspect was that, by crossing the English Channel, she was also entering one of the most hostile and misogynistic environments her career would ever know.

Photograph 51: The Shot That Rewrote Biology

Before we get down to business, it is important to understand two tools that will be the protagonists of this story.

• X-rays
• X-ray crystallography

X-rays are a type of electromagnetic wave, similar to the light we see with our eyes, but invisible to us. They have much more energy and a wavelength the size of an atom. That is why they penetrate the skin and allow medical X-rays, and that is why they can collide with individual atoms and bounce off them.

X-ray crystallography takes advantage of precisely that: if you shine a beam onto an ordered sample, the atoms deflect the beam in specific directions and form a pattern of spots on a photographic film. This pattern is not a picture of the molecule, but a geometric fingerprint from which, with a fair amount of mathematics, the exact position of each atom can be reconstructed. It's like deducing the shape of an invisible object by looking only at the shadow it casts.

In January 1951, Rosalind Franklin arrived at King's College London with a three-year fellowship and a clear mission: to apply her mastery of this technique to the study of a molecule that was then an enigma, deoxyribonucleic acid, or DNA. It was known to be in chromosomes and to have something to do with heredity, but its exact shape was a mystery. And without shape, there is no function: in molecular biology, structure is the mechanism.

The problem with DNA was twofold. It is not a clean crystal like salt or quartz, but a long, flexible fiber, difficult to order. Furthermore, it was extremely sensitive to humidity.

Here came Franklin's first silent discovery: she found that DNA did not have just one form, but two. Below 75% relative humidity, it adopted a short, compact conformation, the A form. Above that, it stretched out and adopted a longer, more open conformation, the B form. Distinguishing them was crucial, because until then other laboratories had worked with mixed samples that produced confusing patterns.

Rosalind designed a special camera that allowed her to control humidity with precision, chose extremely fine fibers from material provided by the Swiss Rudolf Signer, and, with obsessive patience, adjusted exposures of more than 60 hours to obtain sharp images. On May 6, 1952, together with her doctoral student Raymond Gosling, she captured the most famous image in the history of biology: Photograph 51. Against a black background, an X formed by light cross-shaped spots appears. To an untrained eye, it is just a pretty smudge. To a crystallographer, that X can only be produced by a helix.

Photograph 51. Rosalind Franklin. Source: https://scarc.library.oregonstate.edu

From Photograph 51 and hundreds of meticulous measurements, Franklin drew conclusions that are now the foundations of modern genetics. She calculated that the helix had a diameter of about 20 angstroms (two millionths of a millimeter), that it completed a full turn every 34 angstroms, and that there were ten base pairs per turn, separated by 3.4 angstroms. She determined that it was not a single helix but a double one, with two strands coiled around each other. And she deduced that the sugar-phosphate backbone, the electrically charged part, was on the outside of the helix, in contact with water, while the nitrogenous bases (adenine, thymine, cytosine, and guanine, the letters of the genetic code) were hidden on the inside. This orientation, contrary to what other researchers defended, is the correct one and is what makes DNA reading and copying possible.

Her laboratory notebooks, dated between 1951 and 1952, show that Franklin had independently arrived at a model remarkably close to the final one. She knew it was a double helix, knew its exact dimensions, and had correctly placed the components. She lacked one last step, understanding how the bases pair between the two strands (the A-T and C-G rule), and one detail, the antiparallel direction of the chains. In her notes from February 1953, written before Watson and Crick published anything, she was already outlining a helical model with two strands, the bases inward and the phosphates outward. She was weeks, perhaps days, away from closing the loop.

What happened next is another story.

The Heist of the Century: How Rosalind Franklin's DNA Was Stolen

To understand what happened, one must know the setting. At King's College, Rosalind shared a roof with Maurice Wilkins, another physicist also researching DNA. Due to an initial misunderstanding by the laboratory director, John Randall, Wilkins believed Franklin had been hired as his assistant, while she clearly understood in writing that she was to lead her own research line with complete independence. The relationship soured from day one and never recovered. Wilkins felt displaced, and Franklin, fed up with the sexist environment at King's, where she couldn't even eat in the men-only faculty dining room, shut herself in her lab with Raymond Gosling and worked independently.

Fifty miles away, at the Cavendish Laboratory in Cambridge, two ambitious researchers had been obsessed for months with solving the structure of DNA: the young American biologist James Watson, 24, and the British physicist Francis Crick, 36. They had no experimental data of their own. Their method was to build models by hand, with rods and balls, and try combinations until they matched what other labs were measuring. Their first attempt, in 1951, was so clumsy that Franklin dismantled it in a technical visit within minutes. Their boss, Lawrence Bragg, expressly forbade them from continuing to work on DNA, considering it King's territory. But they did not give up.

In late January 1953, Maurice Wilkins received James Watson in his office. Without asking Franklin for permission, he took Photograph 51 (which Gosling had shared with him months earlier, after Franklin announced she would leave King's College) from a drawer and showed it to Watson. Watson, as he himself would later recount in his book The Double Helix, felt his pulse quicken. The answer was in that image. He returned to Cambridge by train and, during the journey, sketched what he had just seen in the margin of a newspaper. The helical X, the dimensions, the symmetry: everything they needed.

The final blow came soon after. Max Perutz, a crystallographer at Cambridge who was part of a British Medical Research Council committee, had access to an internal report written by Franklin in late 1952 with the exact quantitative data of her work: dimensions, angles, crystal symmetry, and precise measurements of the B form of DNA. Perutz passed this report to Crick. Franklin was not informed. Nor was her permission requested. With Photograph 51 in one hand and the numerical data from the report in the other, Watson and Crick built the double helix model in a few weeks. It matched point by point what Franklin was about to publish.

On April 25, 1953, exactly 73 years ago today, the journal Nature published three consecutive articles on the structure of DNA. The first, authored by Watson and Crick, was the triumphant model of the double helix. The other two, authored by Wilkins and by Franklin and Gosling respectively, presented the experimental data that supported the model. The layout subtly implied, through typography, that the latter two were secondary supports to the main “discovery.” In reality, it was the other way around: the model was built on that data, not vice versa. Watson and Crick acknowledged in a footnote that they had been “stimulated” by the work of Wilkins and Franklin. An English elegance for not saying that without them, they would have had absolutely nothing.

Franklin never fully knew what had happened. By the time the model was published, she had already left King's College and was working at Birkbeck on something else: the structure of viruses, where she would again do leading science. She accepted Watson and Crick's model gracefully, never suspecting it had been built with her own data. She died in April 1958, at 37, of ovarian cancer almost certainly caused by prolonged exposure to the X-rays from her experiments. She did not live to see what would come next.

Four years later, in October 1962, the Swedish Academy announced the Nobel Prize in Physiology or Medicine. It was awarded to three men: James Watson, Francis Crick, and Maurice Wilkins, "for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material." The Nobel statutes prohibit awarding the prize posthumously, so the committee could hide behind a formal excuse. But they could also have waited, they could have mentioned Franklin in the acceptance speech or in the nomination. They did not. None of the three laureates uttered her name in their acceptance speeches. Wilkins, who knew exactly what had happened, made only a generic allusion to "our collaborators." Watson, in The Double Helix (1968), portrayed Franklin as an unpleasant, poorly dressed, and difficult woman, whom he contemptuously nicknamed "Rosy." The book, a bestseller, cemented that caricature in the collective memory for decades.

Thus, the woman who took the most important photograph in 20th-century biology died ignored by the scientific community, was erased from the discovery narrative, and, to top it all, was ridiculed by one of the men who took her Nobel.

The heist of the century wasn't just about data. It was about credit, memory, and justice.

Posthumous Justice

For years, Rosalind Franklin's name was a footnote in biology textbooks. It took time, a new generation of women scientists and historians, and, above all, much persistence for her figure to begin to occupy the place she deserved.

The first step came in 1975, when her friend and biographer Anne Sayre published Rosalind Franklin and DNA, a book that dismantled point by point the caricature Watson had cemented in The Double Helix. From then on, other biographers like Brenda Maddox (Rosalind Franklin: The Dark Lady of DNA, 2002) reconstructed her work from notebooks, letters, and testimonies, and demonstrated, with documents in hand, how decisive her contribution had been.

Today, her legacy is everywhere.

• Imperial College London, the University of Cambridge, and King's College itself have buildings, scholarships, and chairs named after her.

• Since 2003, the Royal Society has awarded the Rosalind Franklin Award to promote the scientific careers of women in science and technology.

• In 2020, during the COVID-19 pandemic, the British mass testing laboratory was officially named Rosalind Franklin Laboratory.

• The European Space Agency named the rover it will send to Mars to search for traces of life after her: a beautiful tribute, because it will precisely seek the molecules she helped to understand.

James Watson himself, now very old, has finally acknowledged in several interviews that Franklin deserved to have shared the Nobel and that his portrayal of her in The Double Helix was unfair. It is a belated, incomplete recognition and, above all, useless for her, who had been underground for more than half a century when it arrived.

But it serves, at least, for new generations of students to know how one of the most important chapters in 20th-century science was truly written.

Rosalind Franklin's story is not just that of a brilliant woman whose Nobel was stolen.

It is the story of all women scientists whose work was made invisible, attributed to others, or reduced to "technical support" in a footnote to a man's discovery.

It is also the story of Lise Meitner, discoverer of nuclear fission, whose Nobel was taken by her collaborator Otto Hahn. Of Jocelyn Bell, discoverer of pulsars, whose Nobel was taken by her thesis supervisor. Of Chien-Shiung Wu, Esther Lederberg, Nettie Stevens, and so many others.

That is why today, April 25, International DNA Day, we do not only celebrate a molecule. We celebrate the woman who first photographed it. And we give her back, even if 73 years late, the light she should never have lost.

 

Why Rosalind Franklin's Discovery Is So Important

Before 1953, DNA was an uncomfortable mystery. It had been known since 1869, thanks to the Swiss Friedrich Miescher, that a substance existed in the cell nucleus, which he called "nuclein," and that it was made of sugars, phosphates, and nitrogenous bases. In 1944, Oswald Avery's experiments with bacteria showed that DNA, and not proteins as many scientists argued, was the material that transmitted hereditary information. In 1950, biochemist Erwin Chargaff discovered that the amount of adenine was always equal to that of thymine, and that of cytosine equal to that of guanine—a huge clue whose meaning no one fully understood. But the essential was missing: no one knew what shape the molecule had. Without structure, there was no mechanism, and without a mechanism, it was impossible to explain how it copies, transmits, and translates into a living being. Biology had been circling a closed enigma for decades.

Franklin's work fundamentally changed that. By determining that DNA was a double helix with the sugar-phosphate backbone on the outside and the bases on the inside, with exact dimensions and two different forms depending on humidity, she suddenly opened the door to understanding how heredity works. The structure, almost by itself, explained the mechanism: if the two strands separate, each can serve as a template to make an identical one, and thus a cell can copy its genetic material before dividing. The base pairing (adenine with thymine, cytosine with guanine) became a chemical code capable of storing information stably and, at the same time, being read and replicated with precision. Within months, what was a centuries-old enigma was transformed into a molecule with a comprehensible function. Biology went from being, in large part, a descriptive science to becoming a molecular and predictive science.

From that point on, practically all modern biotechnology is a direct debt to that discovery. The ability to read DNA sequences led to molecular genetics, the Human Genome Project, completed in 2003, and the genetic diagnosis of diseases. PCR, the technique that allows DNA fragments to be multiplied and became world-famous with COVID-19 tests, is based on taking advantage of the exact property made possible by the double helix: separating the strands and copying them. Messenger RNA vaccines that changed the course of multiple diseases, gene therapies that now cure previously incurable hereditary diseases like spinal muscular atrophy, genomic editing with CRISPR, personalized medicine based on each patient's genetic profile, paternity tests, forensic identification of criminals and victims, precision agriculture with modified crops, the synthesis of human insulin in bacteria, or the recent reconstruction of the Neanderthal genome: all of this stems from the same point, a black and white image taken in a London basement in May 1952.

If 20th-century science has a totem molecule, it is the double helix. And if that double helix has a mother, that mother is Rosalind Franklin. The fact that her name took half a century to appear in textbooks does not change the most important fact of all: without her work, modern biology, as we know it, simply would not exist.

DNA Explained for Dummies

DNA (deoxyribonucleic acid) is the instruction manual for every living being. It is inside the nucleus of each of your cells and stores, in the form of a chemical code, everything necessary to build and maintain you: the color of your eyes, your height, how your body digests food, or how your immune system defends itself against a virus. If we could stretch the DNA from a single human cell, it would measure about two meters. And all humans share more than 99% of the same manual; the small remaining differences are what make us unique.

Its shape is the famous double helix: two long chains coiled around each other, like a spiral staircase. The sides of the staircase are a sugar and phosphate backbone. The rungs are made up of four chemical pieces called nitrogenous bases: adenine (A), thymine (T), guanine (G), and cytosine (C). The bases always pair in the same way, A with T and G with C, which makes the two chains fit together like a zipper and, when a cell needs to copy its DNA to divide, it simply unzips and reconstructs each side separately.

The sequence of these four letters, A-T-G-C, is what contains the information. It works like an alphabet: the order in which they are written determines what will be produced. What is produced are proteins, the molecules that do practically all the work in the body (form muscles, transport oxygen, digest food, fight infections). Proteins, in turn, are made of smaller pieces called amino acids, of which there are 20 different types.

How do the four letters of DNA relate to the 20 amino acids? Through a three-letter code called the genetic code. Each group of three consecutive bases (a "triplet" or codon) corresponds to a specific amino acid. For example, the triplet ATG indicates "start manufacturing and put a methionine," GCA means "put an alanine," TTT means "put a phenylalanine," and so on. The cell reads the DNA three letters at a time, translates each triplet into its amino acid, links them in a chain, and when finished, has manufactured a protein. It is, literally, a language: four letters combined into three-letter words form sentences (genes) that, read in order, build a living being.

DNA in a mental image

        DNA Double Helix
    ┌────────────────────────┐
    │                        │
    │   A ══ T               │
    │   │    │               │
    │   T ══ A   ← rungs     │
    │   │    │     (bases)   │
    │   G ≡≡ C               │
    │   │    │               │
    │   C ≡≡ G               │
    │   │    │               │
    │   A ══ T               │
    │   ↑    ↑               │
    │  sugar+phosphate       │
    │  (outer backbone)      │
    └────────────────────────┘

    Reading by triplets (codons):
    A T G │ G C A │ T T T │ C C G
     ↓      ↓       ↓       ↓
    Met   Ala    Phe    Pro  → protein

    Golden rules:
    • A always pairs with T
    • G always pairs with C
    • 3 letters = 1 amino acid
    • Many amino acids = 1 protein
    • Many proteins = 1 living being

Infographic

FAQs. Frequently asked questions about Rosalind Franklin

Who really discovered DNA?

DNA was first isolated as a molecule by Friedrich Miescher in 1869, but its double helix structure was revealed in 1953 thanks to the X-ray crystallography data produced by Rosalind Franklin, which Watson and Crick used without her knowledge or consent to build their final model.

What is Photograph 51 and why does it matter?

Photograph 51 is an X-ray diffraction image taken in 1952 by Rosalind Franklin and her student Raymond Gosling. It captured, with unprecedented clarity, the X-shaped pattern of a helix and allowed researchers to infer the diameter, pitch and helical geometry of the DNA molecule.

How did Watson and Crick gain access to Rosalind Franklin’s data?

Maurice Wilkins, Franklin’s colleague at King’s College London, showed Photograph 51 to James Watson in January 1953 without her permission. Shortly after, Max Perutz handed Watson and Crick an internal Medical Research Council report containing Franklin’s quantitative measurements, which proved decisive in building the double helix model.

Why did Rosalind Franklin not receive the Nobel Prize?

The 1962 Nobel Prize in Physiology or Medicine went to Watson, Crick and Wilkins for the structure of DNA. Franklin had died in 1958 from ovarian cancer, and the Nobel Foundation does not award posthumous prizes, which formally excluded her. Even so, her contribution was not acknowledged in the acceptance speeches.

What is X-ray crystallography?

It is a technique that fires X-rays at a crystal and analyses the diffraction pattern produced as atoms scatter the beam. From that pattern, scientists reconstruct the three-dimensional position of each atom, which makes it possible to determine the structure of molecules as complex as proteins or nucleic acids.

What is the DNA double helix in simple terms?

DNA is a long ladder twisted around itself. The sides are made of sugars and phosphates, and the rungs are pairs of nitrogenous bases (adenine with thymine, cytosine with guanine) held together by hydrogen bonds. This geometry allows genetic information to be copied with remarkable accuracy.

How has the injustice toward Rosalind Franklin been addressed?

Since Anne Sayre’s biography in 1975 and Brenda Maddox’s in 2002, her legacy has been recovered through books, documentaries, the Royal Society’s Rosalind Franklin Award, the UK SARS-CoV-2 sequencing laboratory bearing her name and the European Space Agency’s Rosalind Franklin Mars rover.

How long is the human DNA molecule if stretched out?

If the DNA inside a single human cell were uncoiled and laid end to end, it would measure roughly two metres (about 6.5 feet). Multiplied by the trillions of cells in the body, the total length of human DNA would reach far beyond the Sun, an estimate often cited by the US National Human Genome Research Institute.

Can DNA be used to store digital data?

Yes. Research groups at institutions such as Harvard, Microsoft Research and the European Bioinformatics Institute have encoded text, images and even entire films into synthetic DNA strands. One gram of DNA can theoretically store around 215 petabytes of information and remain readable for thousands of years if kept dry and cold.

Is consumer DNA testing reliable for health predictions?

Direct-to-consumer DNA tests can offer interesting ancestry insights, but their predictive value for complex diseases is limited. Bodies such as the FDA and the NHS recommend confirming any clinically relevant result with a certified genetic test and a qualified genetic counsellor before making medical decisions.