This Day In History: 02/28/1953 - DNA Structure Discovered

This Day In History: 02/28/1953 - DNA Structure Discovered

On February 28th many historical events occurred. These events are recapped by Russell Mitchell in this video clip from "This Day in History". The discovery of DNA by James Watson and Frances Crick being a major one for the scientific community. Not only was DNA discovered on this day, but the Republican Party was founded in Wisconsin. The well-known album Thriller by Michael Jackson won eight Emmy awards as well.


What is the DNA double helix?

Scientist use the term "double helix" to describe DNA's winding, two-stranded chemical structure. This shape - which looks much like a twisted ladder - gives DNA the power to pass along biological instructions with great precision.

To understand DNA's double helix from a chemical standpoint, picture the sides of the ladder as strands of alternating sugar and phosphate groups - strands that run in opposite directions. Each "rung" of the ladder is made up of two nitrogen bases, paired together by hydrogen bonds. Because of the highly specific nature of this type of chemical pairing, base A always pairs with base T, and likewise C with G. So, if you know the sequence of the bases on one strand of a DNA double helix, it is a simple matter to figure out the sequence of bases on the other strand.

DNA's unique structure enables the molecule to copy itself during cell division. When a cell prepares to divide, the DNA helix splits down the middle and becomes two single strands. These single strands serve as templates for building two new, double-stranded DNA molecules - each a replica of the original DNA molecule. In this process, an A base is added wherever there is a T, a C where there is a G, and so on until all of the bases once again have partners.

In addition, when proteins are being made, the double helix unwinds to allow a single strand of DNA to serve as a template. This template strand is then transcribed into mRNA, which is a molecule that conveys vital instructions to the cell's protein-making machinery.

Scientist use the term "double helix" to describe DNA's winding, two-stranded chemical structure. This shape - which looks much like a twisted ladder - gives DNA the power to pass along biological instructions with great precision.

To understand DNA's double helix from a chemical standpoint, picture the sides of the ladder as strands of alternating sugar and phosphate groups - strands that run in opposite directions. Each "rung" of the ladder is made up of two nitrogen bases, paired together by hydrogen bonds. Because of the highly specific nature of this type of chemical pairing, base A always pairs with base T, and likewise C with G. So, if you know the sequence of the bases on one strand of a DNA double helix, it is a simple matter to figure out the sequence of bases on the other strand.

DNA's unique structure enables the molecule to copy itself during cell division. When a cell prepares to divide, the DNA helix splits down the middle and becomes two single strands. These single strands serve as templates for building two new, double-stranded DNA molecules - each a replica of the original DNA molecule. In this process, an A base is added wherever there is a T, a C where there is a G, and so on until all of the bases once again have partners.

In addition, when proteins are being made, the double helix unwinds to allow a single strand of DNA to serve as a template. This template strand is then transcribed into mRNA, which is a molecule that conveys vital instructions to the cell's protein-making machinery.


Friedrich Miescher and the discovery of DNA

Over the past 60 years, DNA has risen from being an obscure molecule with presumed accessory or structural functions inside the nucleus to the icon of modern bioscience. The story of DNA often seems to begin in 1944 with Avery, MacLeod, and McCarty showing that DNA is the hereditary material. Within 10 years of their experiments, Watson and Crick deciphered its structure and yet another decade on the genetic code was cracked. However, the DNA story has already begun in 1869, with the young Swiss physician Friedrich Miescher. Having just completed his education as a physician, Miescher moved to Tübingen to work in the laboratory of biochemist Hoppe-Seyler, his aim being to elucidate the building blocks of life. Choosing leucocytes as his source material, he first investigated the proteins in these cells. However, during these experiments, he noticed a substance with unexpected properties that did not match those of proteins. Miescher had obtained the first crude purification of DNA. He further examined the properties and composition of this enigmatic substance and showed that it fundamentally differed from proteins. Due to its occurrence in the cells' nuclei, he termed the novel substance "nuclein"--a term still preserved in today's name deoxyribonucleic acid.


This Day In History: 02/28/1953 - DNA Structure Discovered - HISTORY

In an article published today in Nature magazine, James D Watson and Francis Crick describe the structure of a chemical called deoxyribonucleic acid, or DNA.

DNA is the material that makes up genes which pass hereditary characteristics from one parent to another.

In short, it consists of a double helix of two strands coiled around each other. The strands are made up of complementary elements that fit together and when uncoiled can produce two copies of the original.

This special property for accurate self-replication allows DNA to duplicate the genes of an organism during the nuclear divisions for growth and the production of germ cells for the next generation.

They began their article with the modest statement: "We wish to suggest a structure for the salt of deoxyribose nucleic acid (DNA). This structure has novel features which are of considerable biological interest."

On 28 February, Mr Crick walked into a Cambridge pub with Mr Watson to celebrate the fact that they had unravelled the structure of DNA, saying: "We have discovered the secret of life!"

The momentous discovery was the culmination of research by Medical Research Council scientists Maurice Wilkins and Rosalind Franklin in London, who produced X-ray diffraction photographs and other evidence.

The discovery opened up some powerful and controversial technologies available today, including genetic engineering, stem cell research and DNA fingerprinting.

Their giant model of a section of DNA, built from laboratory clamps and pieces of metal, is now in the Science Museum in London.

Dr Watson gave a popular account of the discovery in The Double Helix published in 1968.

He also helped launch the Human Genome Project which has sought to understand the meaning of the "life code" contained in the long molecule that resembles a twisted ladder.

Rosalind Franklin died of cancer in April 1958, aged just 37, and as such never received a Nobel Prize for her crucial work in the discovery of DNA.

Francis Crick died in July 2004, aged 88 years, and Maurice Wilkins died in October 2004, also aged 88.


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1937 – Florence Bell arrives in William Astbury’s lab and takes the first X-ray images of DNA. Astbury makes an attempt at a structure the following year.

1944 – Oswald Avery, Colin MacLeod and Maclyn McCarty demonstrate that DNA is the material controlling inheritance.

1952 – Rosalind Franklin takes ‘Photo 51’, a highly detailed image of the ‘B’ or hydrated form of DNA. The photo is later seen by James Watson without her knowledge.

Read more about the discovery of DNA:

1953 – James Watson and Francis Crick propose a model for the structure of the DNA molecule.

They publish the structure in the scientific journal Nature and suggest that the structure indicates DNA’s function.

1972 – DNA from two different organisms is spliced together for the first time by Paul Berg, paving the way for genetic modification and GM foods.

1996 – Dolly the sheep is born. Dolly is the first mammal cloned from a non-embryonic cell. Her DNA is identical to the sheep she was cloned from.


Rosalind Franklin developed her interest in science at school, and by age 15 she decided to become a chemist. She had to overcome the opposition of her father, who did not want her to attend college or become a scientist he preferred that she go into social work. She earned her Ph.D. in chemistry in 1945 at Cambridge.

After graduating, Rosalind Franklin stayed and worked for a while at Cambridge and then took a job in the coal industry, applying her knowledge and skill to the structure of coal. She went from that position to Paris, where she worked with Jacques Mering and developed techniques in x-ray crystallography, a leading-edge technique to explore the structure of the atoms in molecules.


History of DNA

Gregor Medel, was known as the "father of modern genetics" he was responsible for discovering the basic principles of heredity, through the use of his monastery garden, through his famous pea experiment he discovered that genes come in pairs and are inherited in distinctive units.

Friedrich Miescher

Friedrich Miescher was the first person to work on DNA. In 1869 he found DNA when working on leucocytes, while investigating the protein cells he found unexpected properties that did not match those of proteins. He originally called DNA "nuclein". At this point of the time there was little or no research on DNA.

Fredrick Griffith

Fredrick Griffith in 1928 performed an experiment demonstrating that bacteria is capable of transferring genetic information this is called transformation. In the experiment he used mice, no- virulent/ rough strain and virulent/smooth strain to see what condition the mice would die under if injected with the strains. At this point of time the research of DNA was up to H. Muller's x-rays that show induce mutations in a dose dependent fashion.

Oswald Avery

Oswald Avery was in the field of immunochemistry he was the first molecular biologist and a pioneer in this field. He is most known for his experiment that isolated DNA as the material of which genes and chromosomes are made. Avery found that the transformation of bacteria was due to DNA, when scientists previously thought traits were carried by proteins.

Barbara McClintock

McClintock discovered transposition and used this information to show that genes are what are responsible for turning physical characteristics on and off. She worked on developing theories to show the suppression and expression of genetic information from one generation of maize plants to the next.

Erwin Chargaff

Erwin Chargaff in 1950 discovered two rules to prove that DNA had a double helical structure. The 1st rule is that DNA had a equal percentage of adenine to thymine and equal percentage of guanine to cytosine. The 2nd rule is adenine and thymine are always paired and can't be cross paired, the same with guanine and cytosine. At the time the research of DNA was at the point where people had just proven that genic material can be transferred between bacterial cells and DNA passes physical and mental characteristics through different generations.

Maurice Wilkins

Maurice Wilkins originally studied biological molecules like DNA and viruses using microscopes. However, in 1951 he started working with Franklin producing x-rays of DNA, which helped Watson and Crick develop their model of DNA. The research was up to Chargaff rules at the time.

Rosalind Franklin

Rosalind Franklin in 1951 she took x-rays of diffraction images of DNA that showed the helical form of the molecule. Her discovery helped Watson and Crick from their model of DNA. At time the research was up to Chargaff rules on how DNA has a double helical structure.

James Watson and Francis Crick

James Watson and Francis Crick worked together in 1953 to build the first three dimensional model of a DNA structure which helped other scientist understand DNA more thoroughly. At this point in time the research on DNA was up to Chargaff rules about DNA having a double helical structure.


Contents

Ancient theories Edit

The most influential early theories of heredity were that of Hippocrates and Aristotle. Hippocrates' theory (possibly based on the teachings of Anaxagoras) was similar to Darwin's later ideas on pangenesis, involving heredity material that collects from throughout the body. Aristotle suggested instead that the (nonphysical) form-giving principle of an organism was transmitted through semen (which he considered to be a purified form of blood) and the mother's menstrual blood, which interacted in the womb to direct an organism's early development. [1] For both Hippocrates and Aristotle—and nearly all Western scholars through to the late 19th century—the inheritance of acquired characters was a supposedly well-established fact that any adequate theory of heredity had to explain. At the same time, individual species were taken to have a fixed essence such inherited changes were merely superficial. [2] The Athenian philosopher Epicurus observed families and proposed the contribution of both males and females of hereditary characters ("sperm atoms"), noticed dominant and recessive types of inheritance and described segregation and independent assortment of "sperm atoms". [3]

In the Charaka Samhita of 300CE, ancient Indian medical writers saw the characteristics of the child as determined by four factors: 1) those from the mother's reproductive material, (2) those from the father's sperm, (3) those from the diet of the pregnant mother and (4) those accompanying the soul which enters into the fetus. Each of these four factors had four parts creating sixteen factors of which the karma of the parents and the soul determined which attributes predominated and thereby gave the child its characteristics. [4]

In the 9th century CE, the Afro-Arab writer Al-Jahiz considered the effects of the environment on the likelihood of an animal to survive. [5] In 1000 CE, the Arab physician, Abu al-Qasim al-Zahrawi (known as Albucasis in the West) was the first physician to describe clearly the hereditary nature of haemophilia in his Al-Tasrif. [6] In 1140 CE, Judah HaLevi described dominant and recessive genetic traits in The Kuzari. [7]

Preformation theory Edit

The preformation theory is a developmental biological theory, which was represented in antiquity by the Greek philosopher Anaxagoras. It reappeared in modern times in the 17th century and then prevailed until the 19th century. Another common term at that time was the theory of evolution, although "evolution" (in the sense of development as a pure growth process) had a completely different meaning than today. The preformists assumed that the entire organism was preformed in the sperm (animalkulism) or in the egg (ovism or ovulism) and only had to unfold and grow. This was contrasted by the theory of epigenesis, according to which the structures and organs of an organism only develop in the course of individual development (Ontogeny). Epigenesis had been the dominant opinion since antiquity and into the 17th century, but was then replaced by preformist ideas. Since the 19th century epigenesis was again able to establish itself as a view valid to this day. [8] [9]

Plant systematics and hybridization Edit

In the 18th century, with increased knowledge of plant and animal diversity and the accompanying increased focus on taxonomy, new ideas about heredity began to appear. Linnaeus and others (among them Joseph Gottlieb Kölreuter, Carl Friedrich von Gärtner, and Charles Naudin) conducted extensive experiments with hybridisation, especially hybrids between species. Species hybridizers described a wide variety of inheritance phenomena, include hybrid sterility and the high variability of back-crosses. [10]

Plant breeders were also developing an array of stable varieties in many important plant species. In the early 19th century, Augustin Sageret established the concept of dominance, recognizing that when some plant varieties are crossed, certain characteristics (present in one parent) usually appear in the offspring he also found that some ancestral characteristics found in neither parent may appear in offspring. However, plant breeders made little attempt to establish a theoretical foundation for their work or to share their knowledge with current work of physiology, [11] although Gartons Agricultural Plant Breeders in England explained their system. [12]

Between 1856 and 1865, Gregor Mendel conducted breeding experiments using the pea plant Pisum sativum and traced the inheritance patterns of certain traits. Through these experiments, Mendel saw that the genotypes and phenotypes of the progeny were predictable and that some traits were dominant over others. [13] These patterns of Mendelian inheritance demonstrated the usefulness of applying statistics to inheritance. They also contradicted 19th-century theories of blending inheritance, showing, rather, that genes remain discrete through multiple generations of hybridization. [14]

From his statistical analysis, Mendel defined a concept that he described as a character (which in his mind holds also for "determinant of that character"). In only one sentence of his historical paper, he used the term "factors" to designate the "material creating" the character: " So far as experience goes, we find it in every case confirmed that constant progeny can only be formed when the egg cells and the fertilizing pollen are off like the character so that both are provided with the material for creating quite similar individuals, as is the case with the normal fertilization of pure species. We must, therefore, regard it as certain that exactly similar factors must be at work also in the production of the constant forms in the hybrid plants."(Mendel, 1866).

Mendel's work was published in 1866 as "Versuche über Pflanzen-Hybriden" (Experiments on Plant Hybridization) in the Verhandlungen des Naturforschenden Vereins zu Brünn (Proceedings of the Natural History Society of Brünn), following two lectures he gave on the work in early 1865. [15]

Pangenesis Edit

Mendel's work was published in a relatively obscure scientific journal, and it was not given any attention in the scientific community. Instead, discussions about modes of heredity were galvanized by Darwin's theory of evolution by natural selection, in which mechanisms of non-Lamarckian heredity seemed to be required. Darwin's own theory of heredity, pangenesis, did not meet with any large degree of acceptance. [16] [17] A more mathematical version of pangenesis, one which dropped much of Darwin's Lamarckian holdovers, was developed as the "biometrical" school of heredity by Darwin's cousin, Francis Galton. [18]

Germ plasm Edit

In 1883 August Weismann conducted experiments involving breeding mice whose tails had been surgically removed. His results — that surgically removing a mouse's tail had no effect on the tail of its offspring — challenged the theories of pangenesis and Lamarckism, which held that changes to an organism during its lifetime could be inherited by its descendants. Weismann proposed the germ plasm theory of inheritance, which held that hereditary information was carried only in sperm and egg cells. [19]

Hugo de Vries wondered what the nature of germ plasm might be, and in particular he wondered whether or not germ plasm was mixed like paint or whether the information was carried in discrete packets that remained unbroken. In the 1890s he was conducting breeding experiments with a variety of plant species and in 1897 he published a paper on his results that stated that each inherited trait was governed by two discrete particles of information, one from each parent, and that these particles were passed along intact to the next generation. In 1900 he was preparing another paper on his further results when he was shown a copy of Mendel's 1866 paper by a friend who thought it might be relevant to de Vries's work. He went ahead and published his 1900 paper without mentioning Mendel's priority. Later that same year another botanist, Carl Correns, who had been conducting hybridization experiments with maize and peas, was searching the literature for related experiments prior to publishing his own results when he came across Mendel's paper, which had results similar to his own. Correns accused de Vries of appropriating terminology from Mendel's paper without crediting him or recognizing his priority. At the same time another botanist, Erich von Tschermak was experimenting with pea breeding and producing results like Mendel's. He too discovered Mendel's paper while searching the literature for relevant work. In a subsequent paper de Vries praised Mendel and acknowledged that he had only extended his earlier work. [19]

After the rediscovery of Mendel's work there was a feud between William Bateson and Pearson over the hereditary mechanism, solved by Ronald Fisher in his work "The Correlation Between Relatives on the Supposition of Mendelian Inheritance".

In 1910, Thomas Hunt Morgan showed that genes reside on specific chromosomes. He later showed that genes occupy specific locations on the chromosome. With this knowledge, Alfred Sturtevant, a member of Morgan's famous fly room, using Drosophila melanogaster, provided the first chromosomal map of any biological organism. In 1928, Frederick Griffith showed that genes could be transferred. In what is now known as Griffith's experiment, injections into a mouse of a deadly strain of bacteria that had been heat-killed transferred genetic information to a safe strain of the same bacteria, killing the mouse.

A series of subsequent discoveries led to the realization decades later that the genetic material is made of DNA (deoxyribonucleic acid) and not, as was widely believed until then, of proteins. In 1941, George Wells Beadle and Edward Lawrie Tatum showed that mutations in genes caused errors in specific steps of metabolic pathways. This showed that specific genes code for specific proteins, leading to the "one gene, one enzyme" hypothesis. [20] Oswald Avery, Colin Munro MacLeod, and Maclyn McCarty showed in 1944 that DNA holds the gene's information. [21] In 1952, Rosalind Franklin and Raymond Gosling produced a strikingly clear x-ray diffraction pattern indicating a helical form. Using these x-rays and information already known about the chemistry of DNA, James D. Watson and Francis Crick demonstrated the molecular structure of DNA in 1953. [22] Together, these discoveries established the central dogma of molecular biology, which states that proteins are translated from RNA which is transcribed by DNA. This dogma has since been shown to have exceptions, such as reverse transcription in retroviruses.

In 1972, Walter Fiers and his team at the University of Ghent were the first to determine the sequence of a gene: the gene for bacteriophage MS2 coat protein. [23] Richard J. Roberts and Phillip Sharp discovered in 1977 that genes can be split into segments. This led to the idea that one gene can make several proteins. The successful sequencing of many organisms' genomes has complicated the molecular definition of the gene. In particular, genes do not always sit side by side on DNA like discrete beads. Instead, regions of the DNA producing distinct proteins may overlap, so that the idea emerges that "genes are one long continuum". [24] [25] It was first hypothesized in 1986 by Walter Gilbert that neither DNA nor protein would be required in such a primitive system as that of a very early stage of the earth if RNA could serve both as a catalyst and as genetic information storage processor.

The modern study of genetics at the level of DNA is known as molecular genetics and the synthesis of molecular genetics with traditional Darwinian evolution is known as the modern evolutionary synthesis.


The Day Scientists Discovered the ‘Secret of Life’

The place: The Eagle, a genial pub and favorite luncheon spot for the staff, students and researchers working at the University of Cambridge’s old Cavendish laboratory on nearby Free School Lane.

The date: Feb. 28, 1953, a day when real, honest-to-goodness history was made.

The pub in Cambridge, England, where James Watson announced he had “discovered the secret of life.”

Two men entered the noisy pub to create even more noise. The first was a tall, gangly, 25-year-old American bacteriologist with uncombed hair named James Watson. The second, Francis Crick, was a 37-year-old British physicist who, according to one of his scientific rivals, looked like “a bookmaker’s rout.”

With booming voices and youthful bravado, the odd duo bragged that they, in the words of Francis Crick — or at least in the memory of James Watson recalling the words of Francis Crick — “We have discovered the secret of life.”

Indeed, they had. That very morning, the two men worked out the double helix structure of deoxyribonucleic acid, better known to every first-grader as DNA.

Mind you, they did not discover DNA. That scientific feat was actually accomplished in 1869 by Friedrich Miescher, a physiological chemist working in Basel, Switzerland. Miescher determined that DNA, a nucleic acid found in the cell’s nucleus, was comprised of sugar, phosphoric acid, and several nitrogen containing bases. But for decades, no one quite knew much about its precise function.

In 1944, a trio of scientists, Oswald Avery, Colin Macleod, and Maclyn McCarty, determined that DNA was the “transforming principle,” the substance that carries genetic information. Nevertheless, there remained many naysayers who felt that the chemical composition of DNA was far too simple to carry such complex data and, instead, argued that proteins must contain the true genetic material.

Proving how the simple brew of chemicals contained in DNA carried such an array of information required an elucidation of its actual structure, echoing a centuries’ old concept in the history of medicine and science that continues to this very day: specifically, one must determine the form of a biological unit before one can begin to understand its function.

Watson and Crick with a DNA model. The pair was
photographed in the Cavendish Laboratory, University of Cambridge, UK, in May 1953.

Watson and Crick worked with three-dimensional models to re-construct the DNA molecule, much as a college student uses those pesky sticks and balls to cram for an organic chemistry exam.

Only 50 miles away, however, a team of scientists at King’s College in London was using a relatively new technique called X-ray crystallography to study DNA. 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 shape. Unbeknownst to Franklin, one of her colleagues let Watson see the image a few days earlier.

Franklin’s DNA picture experimentally confirmed the correctness of the theoretical double helical model Watson and Crick were developing. As Watson later reflected on the importance of Feb. 28, 1953: “The discovery was made on that day, not slowly over the course of the week. It was simple instantly you could explain this idea to anyone. You did not have to be a high-powered scientist to see how the genetic material was copied”.

They finished building their now-famous model on March 7, 1953.

Watson and Crick published their findings in the April 25, 1953, issue of Nature. It was a brief communication that discussed the double helix of DNA and suggested that the two strands of DNA allowed it to create identical copies of itself. Regardless of the report’s brevity, the announcement changed the world of medicine and science forever.

Rosalind Franklin. Photo coutesy of the Henry Grant Archive/Museum of London.

Tragically, in 1958 Rosalind Franklin died of ovarian cancer. She was 37 years old. Watson and Crick, along with Maurice Wilkins (the colleague of Franklin’s who showed Crick her data), won the Nobel Prize for Medicine or Physiology in 1962. But because the Prize rules prevent it from being awarded posthumously, Franklin did not receive the credit she so richly deserved until years after her death.

In his 1968 memoir, “The Double Helix,” James Watson discusses his less-than-gentlemanly rivalry with Rosalind Franklin as well the appreciation he came to acquire for her brilliant work. Gallant, perhaps, but the credit was a dollar short and quite a few days too late.

Feb. 28, 1953, was a landmark day in human history, medicine and science as well as a transformative moment in the lives of Watson and Crick. Sadly, it was just another day in the laboratory for the unsung Rosalind Franklin.

Dr. Howard Markel is the director of the Center for the History of Medicine and the George E. Wantz Distinguished Professor of the History of Medicine at the University of Michigan.

He is the author or editor of 10 books, including “Quarantine! East European Jewish Immigrants and the New York City Epidemics of 1892,” “When Germs Travel: Six Major Epidemics That Have Invaded America Since 1900 and the Fears They Have Unleashed” and “An Anatomy of Addiction: Sigmund Freud, William Halsted, and the Miracle Drug Cocaine.”

Related Content

Do you have a question for Dr. Markel about how a particular aspect of modern medicine came to be? Send them to us at [email protected]


February 28: The Day Scientists Discovered the Double Helix

The place: The Eagle, a genial pub and favorite luncheon spot for the staff, students and researchers working at the University of Cambridge's old Cavendish laboratory on nearby Free School Lane.

The date: Feb. 28, 1953, a day when real, honest-to-goodness history was made.

Two men entered the noisy pub to create even more noise. The first was a tall, gangly, 25-year-old American bacteriologist with uncombed hair named James Watson. The second, Francis Crick, was a 37-year-old British physicist who, according to one of his scientific rivals, looked like "a bookmaker's rout."

With booming voices and youthful bravado, the odd duo bragged that they, in the words of Francis Crick -- or at least in the memory of James Watson recalling the words of Francis Crick -- "We have discovered the secret of life."

Indeed, they had. That very morning, the two men worked out the double helix structure of deoxyribonucleic acid, better known to every first-grader as DNA.

Mind you, they did not discover DNA. That scientific feat was actually accomplished in 1869 by Friedrich Miescher, a physiological chemist working in Basel, Switzerland. Miescher determined that DNA, a nucleic acid found in the cell's nucleus, was comprised of sugar, phosphoric acid, and several nitrogen containing bases. But for decades, no one quite knew much about its precise function.

In 1944, a trio of scientists, Oswald Avery, Colin Macleod, and Maclyn McCarty, determined that DNA was the "transforming principle," the substance that carries genetic information. Nevertheless, there remained many naysayers who felt that the chemical composition of DNA was far too simple to carry such complex data and, instead, argued that proteins must contain the true genetic material.

Proving how the simple brew of chemicals contained in DNA carried such an array of information required an elucidation of its actual structure, echoing a centuries' old concept in the history of medicine and science that continues to this very day: specifically, one must determine the form of a biological unit before one can begin to understand its function.

Watson and Crick worked with three-dimensional models to re-construct the DNA molecule, much as a college student uses those pesky sticks and balls to cram for an organic chemistry exam.

Only 50 miles away, however, a team of scientists at King's College in London was using a relatively new technique called X-ray crystallography to study DNA. 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 shape. Unbeknownst to Franklin, one of her colleagues let Watson see the image a few days earlier.

Franklin's DNA picture experimentally confirmed the correctness of the theoretical double helical model Watson and Crick were developing. As Watson later reflected on the importance of Feb. 28, 1953: "The discovery was made on that day, not slowly over the course of the week. It was simple instantly you could explain this idea to anyone. You did not have to be a high-powered scientist to see how the genetic material was copied".

They finished building their now-famous model on March 7, 1953.

Watson and Crick published their findings in the April 25, 1953, issue of Nature. It was a brief communication that discussed the double helix of DNA and suggested that the two strands of DNA allowed it to create identical copies of itself. Regardless of the report's brevity, the announcement changed the world of medicine and science forever.

Tragically, in 1958 Rosalind Franklin died of ovarian cancer. She was 37 years old. Watson and Crick, along with Maurice Wilkins (the colleague of Franklin's who showed Crick her data), won the Nobel Prize for Medicine or Physiology in 1962. But because the Prize rules prevent it from being awarded posthumously, Franklin did not receive the credit she so richly deserved until years after her death.

In his 1968 memoir, "The Double Helix," James Watson discusses his less-than-gentlemanly rivalry with Rosalind Franklin as well the appreciation he came to acquire for her brilliant work. Gallant, perhaps, but the credit was a dollar short and quite a few days too late.

Feb. 28, 1953, was a landmark day in human history, medicine and science as well as a transformative moment in the lives of Watson and Crick. Sadly, it was just another day in the laboratory for the unsung Rosalind Franklin.

Dr. Howard Markel is the director of the Center for the History of Medicine and the George E. Wantz Distinguished Professor of the History of Medicine at the University of Michigan.

He is the author or editor of 10 books, including "Quarantine! East European Jewish Immigrants and the New York City Epidemics of 1892," "When Germs Travel: Six Major Epidemics That Have Invaded America Since 1900 and the Fears They Have Unleashed" and "An Anatomy of Addiction: Sigmund Freud, William Halsted, and the Miracle Drug Cocaine."

This article, reprinted with permission from PBS Newshour, was originally published on February 28, 2013.


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