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How Rosalind Franklin Discovered DNA Structure

In the early 1950s, the race was on to discover the structure of DNA, as a series of scientific discoveries began to disprove previous theories of heredity, including discoveries by a Swiss chemist named Friedrich Miescher, who identified DNA in 1869. Yet, while many of us may attribute the discovery of the structure of DNA to James Watson, Francis Crick, and Maurice Wilkins, there was another influential and important scientist behind the discovery: Rosalind Franklin, who discovered a crucial piece of information about the structure of DNA. However, despite the importance of those discoveries, Franklin was never credited, and Watson, Crick, and Wilkins went on to win the Nobel Prize, years after her death. Yet, to this day, many people wonder about the data stolen from Rosalind Franklin, and whether that was an act of sexism in scientific research.

This was Rosalind Franklin in Paris, France! Image Source

The early life and education of Rosalind Franklin

Rosalind Elsie Franklin was born on July 25, 1920 to an influential Anglo-Jewish family in London, England. She attended St. Paul’s School for Girls, which emphasized on the importance of preparing for careers.

Her mother, Muriel Waley, noted that “all her life knew exactly where she was going and took science for her subject,” as at 15 years old, she knew she wanted to be a scientist, and she was also extremely intelligent, particularly in math, science, and languages.

In 1938, she began studying physical chemistry at Newnham College in Cambridge, and graduated with Second Class Honors. After graduation, she received a fellowship to conduct research at the University of Cambridge. However, when working on a project assigned by her supervisor, Ronald George Wreyford Norrish, she noticed a fundamental error in the project that caused an argument as Norrish refused to accept her findings.

He later noted that he did not approve of her “raising the status of her sex to equality with men.” In 1942, at a time when World War II was going on, Franklin decided to work for the British Coal Utilisation Research Association and contribute to war efforts by researching the chemistry of coal and carbon. During her time in coal research, she wrote her doctoral thesis, titled “The Physical Chemistry of Solid Organic Colloids with Special Reference to Coal and Related Materials,” and received her PhD from the University of Cambridge.

“…All her life knew exactly where she was going and took science for her subject.”

Muriel Waley, Rosalind Franklin’s mother
This was Maurice Wilkins, who suggested that Franklin use x-ray diffraction methods to study DNA! Image Source

Rosalind Franklin’s work with x-ray diffraction

After earning her PhD, she went on to work at the Laboratoire Central des Services Chimique de l’Etat in Paris led by Jacques Mering, where she learned to analyze carbon using x-ray diffraction techniques, which would prove to be useful during her research on the structure of DNA. While she achieved recognition among her friends and developed many relationships in France, she began to search for work in England, and soon, she received a fellowship for John T. Randall’s biophysics unit at King’s College, where she was told that she would work with Raymond Gosling to analyze proteins using the x-ray diffraction methods. However, another scientist in the laboratory, Maurice Wilkins, was doing work on DNA samples, and wanted to work with Franklin to test the samples using x-ray diffraction. This was not well communicated to Franklin, since she expected to mostly work alone, so Wilkins and Franklin did not work well together, because of their differing personalities and miscommunication, with Wilkins’ reserved and shy personality compared to Franklin, who was confrontational and thrived on intellectual debates.

The discovery of the double helix

From the late 19th century to the 1950s, scientific discoveries in DNA spurred interest in the discovery of the structure of DNA, as in 1866, a Swiss chemist named Friedrich Miescher began researching human white blood cells, and discovered that the cells contained a unique substance, which he called “nuclein.” This substance would soon be discovered to be DNA, and in 1943, Oswald Avery would prove that DNA was the molecule that carried genetic information. However, in 1929, Phoebus Levene discovered the base nucleotide pairs that RNA was made of, which includes adenine, cytocide, guanine, and uracil. His work was important to the discovery of the structure of DNA, as scientists now knew that DNA was made up of base pairs. In addition, Erwin Chargaff discovered what is now known as Chargaff’s Rule, which stated that adenine always pairs with thymine, and cytosine always pairs with guanine.

With the race to discover the structure of DNA, there were many teams around the world scrambling to find this discovery, most notably a team at the Cavendish Laboratory in Cambridge, consisting of James Watson and Francis Crick, as well as Rosalind Franklin and Maurice Wilkins, who were studying the structure of DNA at King’s College.

This is the famous “Photo 51” taken by Rosalind Franklin and Raymond Gosling! Image Source

The famous “Photo 51”

While the team at Cambridge constructed ideas for the DNA model with a cardboard stick-and-ball model using data published by other scientists, Wilkins suggested that Franklin study DNA with x-ray crystallography to help understand its physical properties. X-ray crystallography is used to study the molecular structure of crystalline materials, since by shining x-rays on crystals, such as crystalized DNA, the ray is deflected to create a pattern on film. With more than 100 hours of x-ray exposure to a dry “A” and wet “B” form of DNA, one of the most important breakthroughs in the race to find the structure of DNA came when Franklin and a graduate student named Raymond Gosling took the famous photo of the wet form of DNA, titled “Photo 51,” which showed the distinctive “X” shape of a helix and consistent dimensions.

From this photo, Franklin was able to find the basic dimensions of DNA and prove that the phosphate groups were on the outside of the structure with the nucleotides inside and using mathematical calculations, and Franklin and Wilkins determined the molecular structure of the wet form of DNA. However, the dry form did not show the same structure, so Franklin decided to refrain from announcing her results before she was able to gather more evidence of the structure of DNA in the dry form.

The impact of “Photo 51” on Watson and Crick’s discovery

Meanwhile, the Cambridge team had used cardboard models to test their theory, initially creating a three-stranded model that was inside out, which was immediately dismissed as incorrect. However, they did not have sufficient evidence to build a model of DNA, until in January, 1953, without Franklin’s knowledge or permission, Wilkins showed Watson “Photo 51,” who immediately recognized the significance of the image, as it showed that DNA was a helical structure. In fact, he stated that when he saw the image, “my mouth fell open and my pulse began to race.” With this critical piece of information and research data collected by other scientists, such as Chargaff, Watson and Crick were able to determine the 3D structure of DNA and publish the results in the Nature journal.

In this model, Watson and Crick stated that the molecule contained two strands that wound around each other like a twisted ladder, and between the strands, it contained monomer nucleotides that paired together as adenine and thymine, cytosine and guanine, which was consistent with Chargaff’s Rule. The two strands of DNA were complementary, so the DNA strand can replicate by separating the two strands and building from one strand. The double helix structure proposed by Watson and Crick was immediately accepted by the scientific community, as it fit perfectly with current research data. In fact, after discovering the structure of DNA, Crick announced, “We had found the secret of life,” and this was quite true, as their discovery was arguably one of the most important scientific breakthroughs in the field of biology. Scientists now understood the key component for heredity, biology, and evolution, and since the discovery of the structure of DNA, scientists have been able to edit the human genome, treat hereditary diseases, conduct genetic testing, as well as many more.

Franklin’s career after the discovery of the structure of DNA

By 1953, Franklin decided to leave King’s College and join J. D. Bernall’s crystallography laboratory at Birkbeck College, where she would go on to lead a team to study the structure of the tobacco mosaic virus (TMV). Using x-ray diffraction techniques, Franklin took photos of the viruses and made additional discoveries, such as establishing the location of the virus’ genetic material. In addition, her expertise in viruses was recognized by the Royal Institution, as her team was asked to build models of viruses for the Brussels World’s Fair in 1958.

By this time, Franklin was one of the best in her field, often being the only female presenter at scientific conferences throughout Europe and the United States. However, despite her success, she still experienced discrimination, as she would often be denied funding, equipment, and job security. While she would become most famous for her work on DNA, she published 19 scientific articles on coal and carbon and 21 on viruses, and her discoveries in those fields were significant.

Unfortunately, in 1956, Franklin was diagnosed with ovarian cancer, which was possibly linked to her work with radiation, and for the next 18 months, she would undergo many surgeries and treatments, but she still continued her research during her periods of remission. Sadly, Rosalind Franklin passed away on April 16, 1958, at the early age of 37.

Did Watson and Crick steal Franklin’s data?

However, one controversy with the discovery of the structure of DNA still remains today. In 1962, James Watson, Francis Crick, and Maurice Wilkins were awarded the Nobel Prize in Physiology or Medicine, but Rosalind Franklin had passed away four years earlier due to ovarian cancer. While some may argue that leaving out Franklin was fair since the Nobel Prize can’t be given posthumously, this rule was only established in 1974, which was 12 years after Watson, Crick, and Wilkins won the Nobel Prize for the discovery of the structure of DNA.

Yet, Franklin never knew about how much Watson and Crick’s work relied on her data. In addition to “Photo 51,” Watson and Crick needed precise numbers about the helix from Franklin’s work in x-ray crystallography, so they obtained the information from Max Perutz, a researcher at Cambridge, who had obtained the information from Franklin. She had actually presented the same information 15 months earlier during a small seminar that Watson had attended, but because of his lack of chemistry knowledge, he had not realized the significance of the data and did not take notes. Nevertheless, the methods used to obtain her data were completely unprofessional and disrespectful, and Watson and Crick did not ask for consent to interpret her work, nor did they acknowledge her contributions in their paper or when they received the Nobel Prize.

Rosalind Franklin
Despite the lack of recognition for her work, Rosalind Franklin will forever be an important inspiration for aspiring female scientists. Image Source

Sexism faced by Franklin

In addition, Crick had later admitted, “I’m afraid we always used to adopt — let’s say, a patronizing attitude towards her,” and women in academia was often frowned upon at the time, as women were not allowed to eat at the university dining area. In James Watson’s autobiography, The Double Helix, Rosalind Franklin was depicted as an ill-tempered, incompetent, arrogant, and jealous scientist nicknamed “Rosy,” and while the book was popular, the description of Franklin sparked outrage among those who knew her, including Maurice Wilkins, Francis Crick, Linus Pauling, who was another scientist that worked on discovering the structure of DNA, and Anne Sayre, a friend of Franklin who later published the book, Rosalind Franklin and DNA, to show the contributions Franklin made to the field of biology.

In fact, J. D. Bernal, an influential pioneer of x-ray crystallography in molecular biology, stated that Franklin had “single-minded devotion to scientific research,” and her career “was distinguished by extreme clarity and perfection in everything she undertook.” However, while Franklin was never recognized for her remarkable work, there is no doubt that her work and understanding of DNA has left a legacy on biology forever. With the issue of sexism and discrimination in science and academia that still exists, Franklin is among the brilliant and exceptional women that changed our understanding of biology and will forever inspire young female scientists with her resilience and determination.

“[Rosalind Franklin’s] single-minded devotion to scientific research… [Her career] was distinguished by extreme clarity and perfection in everything she undertook…ingenious experimental and mathematical techniques of X-ray analysis”

J. D. Bernal, pioneer in x-ray crystallography in molecular biology


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