Annotated version of the Watson and Crick article (2023)

Reprinted with permission fromNaturemagazine

A structure for the nucleic acid of deoxyribose
JD Watson e FHC Crick (1)

April 25, 1953

(2), Nature (3), 171, 737-738We would like to propose a structure for the deoxyribose nucleic acid salt (D.N.A.). This structure has novel features that are of considerable biological interest.A structure for nucleic acid has already been proposed bypaula (4)e Corey1🇧🇷 They kindly provided us with their manuscript prior to publication. His model consists of three intertwined chains, with the phosphates close to the fiber axis and the bases on the outside. In our opinion, this structure is unsatisfactory for two reasons:(1) We believe that the material providing the X-ray patterns is the salt, not the free acid. Without the acidic hydrogen atoms, it's not clear what forces would hold the structure together, especially since the negatively charged phosphates repel each other near the axis.(2) Some of the van der Waals distances look very small.Fraser also proposed another three-chain structure (in press). In his model, the phosphates are on the outside and the bases on the inside, connected by hydrogen bonds. This described structure is rather ill-defined and therefore we will not comment on it.

We would like to propose a radically different structure for deoxyribose nucleic acid salt (5).This structure has two helical chains, each wound around the same axis (see diagram). We made the usual chemical assumptions that each chain consists of phosphate diester groups connecting beta-D-deoxyribofuranose residues with 3',5' linkages. The two strands (but not their bases) are connected by a dyad perpendicular to the fiber axis. Both chains follow right-handed helices, but because of the dyad, the sequences of atoms are inthe two currents run in opposite directions (6)🇧🇷 Each string vaguely resemblesde Furberg2Model No. 1 (7)🇧🇷 That is, the bases are inside the helix and the phosphates are outside. The configuration of the sugar and nearby atoms approximates Furberg's "standard configuration", with the sugar approximately perpendicular to the attached base. There is one residue every 3.4 Az-Direction. We assume an angle of 36° between adjacent residues on the same strand, so that the structure is repeated after 10 residues on each strand, that is, after 34 Å. The distance of a phosphorus atom from the fiber axis is 10 Å. Since the phosphates are outside, the cations have easy access to them.

Annotated version of the Watson and Crick article (1) illustration 1
This illustration is purely schematic.(8)🇧🇷 The two strands symbolize the two sugar-phosphate chains and the horizontal bars the base pairs that hold the chains together. The vertical line marks the fiber axis.

The structure is open and its water content is quite high. At lower water levels, we would expect the foundations to slope, allowing the structure to become more compact.

The novel feature of the structure is the way the two chains are held together by the purine and pyrimidine bases. The base planes are perpendicular to the fiber axis. They are attached to each other in pairs, with a single base on one strand hydrodividing to a single base on the other strand, such that the two are identically adjacent.z-Coordinates. One of the pairs must be a purine and the other a pyrimidine for binding to occur. Hydrogen bonds are formed as follows: purine position 1 to pyrimidine position 1; Purine position 6 to pyrimidine position 6.

Assuming that the bases in the structure occur only in the most plausible tautomeric forms (ie, with the keto configuration instead of the enol), it turns out that only certain pairs of bases can bind.These pairs are: adenine (purine) with thymine (pyrimidine) and guanine (purine) with cytosine (pyrimidine) (9).

In other words, if an adenine on either chain forms one member of a pair, then under these assumptions the other member must be thymine; similar for guanine and cytosine. The single-stranded base sequence does not appear to be constrained in any way. However, if only certain base pairs can be formed, it follows that, given the sequence of bases on one strand, the sequence on the other strand is automatically determined.

It has been found experimentally3,4that the ratio of amounts of adenine to thymine and the ratio of guanine to cytosine to deoxyribose nucleic acid are always very close to one.

It is probably impossible to build this structure using ribose sugar instead of deoxyribose, as the extra oxygen atom would make very close van der Waals contact.

Previously published X-ray data5,6for deoxyribose nucleic acid are insufficient for a rigorous test of our structure. As far as we can tell, it's more or less consistent with the experimental data, but it should be considered unproven until verified with more accurate results.Some of them are collected in the following communications (10)🇧🇷 we wereI did not know the details of the results presented there when we designed our structure (11), based primarily, though not entirely, on published experimental data and stereochemical arguments.

It has not escaped our attention.(12)that the specific pairing we postulate points directly to a possible genome copying mechanism.Full details of the structure, including the conditions assumed during construction, together with a set of coordinates for the atoms,will be published elsewhere (13).We are very grateful to Jerry Donohue for his constant advice and criticism, particularly regarding interatomic distances. Knowledge of the general nature of the unpublished experimental results and Drs. M.H.F. Wilkins, Dr. R. E. Franklin and his associates at King's College London. One of us (J.D.W.) was supported by a grant from the National Foundation for Childhood Paralysis.1Pauling, L.y Corey, R.B.,Nature,171, 346 (1953);Proc. Nac. USA Academic Science,39, 84 (1953).
2Furberg, S.,Acta Chem. Scan.,6, 634 (1952).
3Chargaff, E., for references see Zamenhof, S., Brawerman, G. and Chargaff, E.,Biochemistry and Biophysics. records9, 402 (1952).
4Wyatt, G. R.,j Gen. Fisiol.36, 201 (1952).
5Astbury, WT, Symp. Society Erw. biological 1, Nucleic Acid, 66 (Camb. Univ. Press, 1947).
6Wilkins, M.H.F., e Randall, J.T.,Biochemistry and Biophysics. records10, 192 (1953).
(Video) (RARE) Interview with James Watson and Francis Crick

Not surprisingly, minutes after their first meeting at the Cavendish Laboratory in Cambridge, England, in 1951, James D. Watson and Francis H. C. Crick were discussing how to find the structure of DNA. Watson, a 23-year-old geneticist, and Crick, a 35-year-old former physicist who studied protein structure for his doctorate in biophysics, considered the architecture of DNA the most important question in biology. Knowing the structure of this molecule would be the key to understanding how genetic information is copied. This, in turn, would lead to finding cures for human illnesses.
Aware of these profound implications, Watson and Crick were obsessed with the problem and, perhaps more than any other scientist, were determined to find the answer first. Their competitive spirit drove them to work fast and undoubtedly helped them succeed in their quest.Watson and Crick's relationship also led to her having quick ideas. They continually discussed the problem and exchanged ideas. This was especially helpful as everyone was inspired by different tests. For example, when a visually sensitive Watson saw a speckled cross-shaped pattern on an X-ray of DNA, he knew that DNA must be a double helix. From data on the symmetry of DNA crystals, Crick, an expert on crystal structure, realized that the two strands of DNA run in opposite directions.Since the breakthrough discovery of the double helix in 1953, Watson has used the same fast, competitive approach to fuel a revolution in molecular biology. As a Harvard professor in the 1950s and 1960s and as the former director and current president of Cold Spring Harbor Laboratory, he tirelessly built intellectual arenas – scientific groups and laboratories – to apply the knowledge gained from the discovery of the double helix to proteins. synthesis. the genetic code and other areas of biological research. By relentlessly advancing these areas, he has also promoted the view among biologists that solving major health problems requires research at the most fundamental level of life.

(2) In this day,Naturepublished the newspaper you are reading.According to historian of science Victor McElheny of the Massachusetts Institute of Technology, this date was a turning point in a long battle between two fields of biology, vitalism and reductionism. Whereas vitalists studied whole organisms and considered genetics too complex to be fully understood, reductionists saw the deciphering of basic life processes as entirely possible and crucial to curing human disease. The discovery of the double helix structure of DNA was a major blow to the vitalist approach and gave impetus to the reductionist field of molecular biology.Historians wonder how the timing of the DNA race affected its outcome. After years of being distracted by the war effort, science was able to focus more on issues like human health. But in the United States it was threatened by restrictions on the free exchange of ideas. Some think that the American explorer Linus would have surpassed Pauling Watson and Crick if Pauling's ability to travel had not been impeded by the overzealous Committee on Un-American Activities in 1952.

(3) Nature(founded in 1869) and hundreds of other academic journals, help advance science by providing researchers with a place to publish and discuss results. Today, journals also validate the quality of this research through a rigorous assessment known as peer review. Typically, at least two scholars, chosen by the journal's editors, assess the quality and originality of each article and recommend whether or not it should be published.Scientific publishing was a different ball game when Watson and Crick submitted this paper.Nature.As there was no formal peer review process in most journals, editors generally made their own decisions about submissions, only seeking informal advice when unfamiliar with a topic.

(4)Trying to figure out the structure of DNA has been a race among many players. They were the world-renowned chemist Linus Pauling of the California Institute of Technology and the X-ray crystallographers Maurice Wilkins and Rosalind Franklin of King's College London, as well as Watson and Crick of the Cavendish Laboratory of the University of Cambridge.

(Video) DNA Journal Article explained- Watson and Crick

The competitive juices were flowing long before the DNA Sprint was in full swing. In 1951, Pauling narrowly defeated scientists at the Cavendish Lab, a leading center for the study of protein structure, with the discovery that certain proteins are spiral-shaped. Defeat hurt. When Pauling submitted a paper for publication in early 1953 proposing a three-stranded DNA structure, Cavendish's boss gave Watson and Crick permission to work on the DNA structure full-time. Cavendish didn't want to lose twice to Pauling.

Pauling's proposed DNA structure was a three-stranded helix with the bases facing outward. Although the model was wrong, Watson and Crick were sure that Pauling would soon discover his error and estimated that he was six weeks away from the correct answer. Electrified by urgency and the prospect of defeating a science superstar, Watson and Crick discovered the double helix after a four-week modeling frenzy.

Pauling was thwarted in his attempts to view X-ray photos of King's College DNA, crucial evidence that inspired Watson's view of the double helix, and had to settle for inferior earlier photos. In 1952, Wilkins and the head of King's laboratory refused Pauling's request to see their photographs. Pauling had planned to attend a scientific meeting in London, where he would likely have renewed his application in person, but Pauling's trip was cut short by the U.S. House Committee on Un-American Activities, citing his anti-war activism. So it was fitting that Pauling, who received the Nobel Prize in Chemistry in 1954, also received the Nobel Peace Prize in 1962, the same year that Watson and Crick were awarded the Nobel Prize for discovering the double helix.

(5)Here, young scientists Watson and Crick call their model "radically different", in stark contrast to the model proposed by scientific powerhouse Linus Pauling. This demand was justified. While the Pauling model was a triple helix with protruding bases, the Watson-Crick model was a double helix with internal bases forming adenine (A) with thymine (T) and cytosine (C) with guanine (G).

(6)That central description of the double helix model remains today, a monumental achievement considering that the vast majority of research has been discarded or modified over time.According to science historian Victor McElheny of the Massachusetts Institute of Technology, the double helix theory is one of Newton's laws of motion because of its longevity. Just as Newtonian physics has survived centuries of scientific scrutiny to become the foundation of today's space programs, since 1953 the double helix model has provided the foundation for many areas of research, including the biochemistry of DNA replication, the decryption of the code genetics and engineering. and the sequencing of the human genome.

(7)Norwegian scientist Sven Furberg's model of DNA, which correctly positions the bases within a helix, was one of many ideas about DNA that helped Watson and Crick infer the structure of the molecule. In a way, they synthesized these ideas. With little lab work, they gathered clues and advice from other experts to find the answer. Watson and Crick's exceptional scientific training, passion and collaboration made them capable of this synthesis.

(8)A visual representation of Watson and Crick's model was crucial in showing how DNA components fit together in a double helix. In 1953, Crick's wife, Odile, drew the diagram used to represent DNA in this article.Scientists use many different types of visual representations of DNA.

(9) The final hurdle for Watson and Crick was figuring out how the four DNA bases pair up without distorting the helix. To visualize the response, Watson constructed cardboard cutouts of the bases. One morning, when Watson was moving sections back and forth on a table, he found that just a combination of basic molecules produced a DNA structure without bulges or extensions. As Crick says in his bookwhat a crazy searchWatson solved the puzzle "not by logic but by chance". Watson and Crick adopted this modeling approach from the eminent chemist Linus Pauling, who used it to successfully discover that some proteins have a helical structure.

(Video) DNA Discoveries Before Watson and Crick

(10) Adjacent to the Watson-Crick article in the April 25, 1953 issueNatureit was a work published separately by King's College scholars Maurice Wilkins and Rosalind Franklin, who worked independently. The Wilkins and Franklin papers described the X-ray crystallographic evidence that helped Watson and Crick develop their structure. The authors of the three articles, their laboratory supervisors, and the editors of theNaturethey agreed that all three would be published in the same issue.

The "following communications" to which our authors refer are the articles by Franklin and Wilkins published in the pages of the journal immediately following the article by Watson and Crick. They (and other documents) can be downloaded as PDF files (Adobe Acrobatmandatory) ofThe nature50 years of DNASite (

Here are the direct links:Molecular configuration in sodium thymonucleate
Franklin, R. e Gosling, R. G.
Nature171, 740-741 (1953)
Molecular structure of deoxypentose nucleic acids
Wilkins, M.H.F., Stokes, A.R. e Wilson, H.R.
Nature171, 738-740 (1953)

(11)That sentence marks what many believe is an inexcusable failure to give King's College scholar Rosalind Franklin proper credit. Watson and Crick say here that they "didn't know" Franklin's unpublished dates, but Watson later admits in his bookthe double helixthat this data was crucial to solving the problem. Watson and Crick knew that this data would be published in the same issue on April 25th.Nature,but they were not officially recognized in their newspaper.

What exactly was this data and how did Watson and Crick get access to it? While they were busy building their models, Franklin worked on the DNA puzzle using X-ray crystallography, which involved X-ray DNA samples to infer its structure. In late February 1953, her analysis of these photos brought her closer to the correct DNA model.

But Franklin was frustrated by an inhospitable environment at King's, which pitted her against her peers. And in an institution that denied women the cafeteria and other social spaces, they were denied access to the informal discourse essential to any scientist's work. Seeing no chance of a decent working life at King's, Franklin decided to take another job. As he prepared to leave, he handed his X-rays to his colleague Maurice Wilkins (an old friend of Crick's).

Then, at perhaps the most crucial moment in the search for the structure of DNA, Wilkins showed Watson one of Franklin's photographs without Franklin's permission. Watson remembers, "As soon as I saw the photo, my mouth caught my eye and my pulse started to race." To Watson, the cross-shaped pattern of spots in the photo meant that the DNA had to be a double helix.

Was it unethical for Wilkins to develop the photos? Should Watson and Crick have credited Franklin for their contribution to this article? Why not? Could Watson and Crick have made their discovery without Franklin's data? Scientists and historians have struggled with these questions for decades.

(Video) Watson-Crick Model of DNA

To read more about Rosalind Franklin and her history with Wilkins, Watson and Crick, check out the following:

"Light on a Dark Lady" by Anne Piper, longtime friend of Franklin's


"The Double Helix and the False Heroin", an essay onThe natureSite Double Helix: 50 anos de DNA.


A review of Brenda Maddox's recent book,Rosalind Franklin: A Dama Sombria do DNAnoThe guard(UNITED KINGDOM)


(12) That phrase, and the phrase it begins with, is perhaps one of the greatest understatements in biology. Watson and Crick then realized that their work had important scientific implications beyond just a "pretty structure". In this statement, the authors say that base pairing in DNA (adenine bonds with thymine and guanine bonds with cytosine) provides the mechanism by which the genetic information carried in the double helix can be accurately duplicated. Knowledge of this copying mechanism triggered a scientific revolution that would lead, among other advances in molecular biology, to the ability to manipulate DNA for genetic engineering and medical research and to decode the human genome along with that of the mouse, yeast, and fruit. flies and other research organisms.

(13) This article is short because it was only intended to announce Watson and Crick's discovery and because they were in a competitive situation. In January 1954 they published the "full details" of their work in a long article (inAnnals of the Royal Society).This "explain later" approach was common in science in the 1950s and still is today. In fact, Rosalind Franklin did the same, supplementing her little April 25 newsletter with two longer articles.

Today, scientists publish their results in a variety of formats. They also present their work at conferences. Watson reported his and Crick's findings at the prestigious annual symposium at Cold Spring Harbor Laboratory in June 1953. As part of our recognition of the fiftieth anniversary of the discovery of the double helix, we will join scientists at Cold Spring Harbor to present their work on theLecture "DNA Biology"..

(Video) The Discovery of the Structure of DNA | AMS OpenMind

© Exploratory


What mistake was made in the Watson and Crick paper from April 1953 that they corrected in future papers? ›

Watson and Crick's model erroneously placed the bases on the outside of the DNA molecule with the phosphates, bound by magnesium or calcium ions, inside. One of the key characteristics of science is that it relies on evidence.

What was the purpose of Watson and Crick's article? ›

Watson and Crick developed their ideas about genetic replication in a second article in Nature, published on May 30, 1953. The two had shown that in DNA, form is function: the double-stranded molecule could both produce exact copies of itself and carry genetic instructions.

Was Watson and Crick's proposal correct? ›

The proposal of Watson and Crick, wherein the DNA is a three-dimensional, double helix structure was accurate. This further indicated that hydrogen bonds exist and hold the complementary bases in pairs.

What facts about DNA does the Watson-Crick model explain notebook? ›

With the aid of illustrations, Watson and Crick state that their model of DNA consists of two helical strands twisted around each other in a double helix. Each strand, the authors explain, contains a chain of repeating units called nucleotides, where each nucleotide contains a sugar, a phosphate group, and a base.

Why was the first proposal of Watson and Crick incorrect? ›

They were misled for a while by an erroneous understanding of how the different elements in thymine and guanine (specifically, the carbon, nitrogen, hydrogen, and oxygen rings) were configured.

Why the triple helix model of DNA was incorrect? ›

This is Linus Pauling's failed attempt to predict the structure of DNA. The problem with his triple helix model is that the phosphates form the helical core, with the bases pointing outwards. This would be impossible under normal cellular conditions.

What are the main features of Watson and Crick model of DNA? ›

In Watson and Crick's model, the two strands of the DNA double helix are held together by hydrogen bonds between nitrogenous bases on opposite strands. Each pair of bases lies flat, forming a "rung" on the ladder of the DNA molecule. Base pairs aren't made up of just any combination of bases.

How did Watson and Crick determine the structure of DNA? ›

Taken in 1952, this image is the first X-ray picture of DNA, which led to the discovery of its molecular structure by Watson and Crick. Created by Rosalind Franklin using a technique called X-ray crystallography, it revealed the helical shape of the DNA molecule.

What is DNA and why was it so important to learn about its structure? ›

DNA contains the instructions needed for an organism to develop, survive and reproduce. To carry out these functions, DNA sequences must be converted into messages that can be used to produce proteins, which are the complex molecules that do most of the work in our bodies.

What is the main weakness in Watson and Crick's paper? ›

The major weaknesses in the Watson and Crick's paper are; 1. They did not give any credit to those that helped them in their research They also did not cite those whose research they had used. Most of the work was drawn by Crick's wife and she was not credited.

What is a mistake in the DNA called? ›

A mutation is a change in the DNA sequence of an organism. Mutations can result from errors in DNA replication during cell division, exposure to mutagens or a viral infection.

What errors can occur in DNA replication? ›

Replication errors can also involve insertions or deletions of nucleotide bases that occur during a process called strand slippage. Sometimes, a newly synthesized strand loops out a bit, resulting in the addition of an extra nucleotide base (Figure 3).

Who really discovered DNA first? ›

The molecule now known as DNA was first identified in the 1860s by a Swiss chemist called Johann Friedrich Miescher. Johann set out to research the key components of white blood cells?, part of our body's immune system. The main source of these cells? was pus-coated bandages collected from a nearby medical clinic.

How does the Watson Crick model explain mutation? ›

Watson and Crick proposed3 that mutations could occur because of “a base occurring very occasionally in one of the less likely tautomeric forms, at the moment when the complementary chain is being formed”. In other words, G·T and A·C mispairs could occur if one of the bases is in a disfavoured tautomeric form (Fig.

Who actually discovered the double helix? ›

In 1962, James Watson, Francis Crick and Maurice Wilkins received the Nobel prize for the discovery of the structure of DNA. Notably absent from the podium was Rosalind Franklin, whose X-ray photographs of DNA contributed directly to the discovery of the double helix.

Why didn't Franklin get a Nobel Prize? ›

Why wasn't Franklin recognized for her contribution? While she didn't share the 1962 Nobel prize she couldn't have - she died four years earlier at the age of 37, a victim of ovarian cancer. Nobel prizes aren't awarded posthumously.

Who discovered DNA as genetic material? ›

Who first identified DNA? Although James Watson and Francis Crick determined the double-helical structure of DNA, DNA itself was identified nearly 90 years earlier by Swiss chemist Friedrich Miescher.

Did Watson and Crick think DNA was a triple helix? ›

Crick and Watson's first model was a triple helix with its bases on the outside of the molecule. The sugar-phosphate backbones ran down the centre, with the phosphate groups of each chain bound to one another by magnesium ions.

Why doesn't the DNA look like a double helix? ›

Under a microscope, the familiar double-helix molecule of DNA can be seen. Because it is so thin, DNA cannot be seen by the naked eye unless its strands are released from the nuclei of the cells and allowed to clump together.

Why is DNA twisted and not straight? ›

The bases in DNA stay on the inside of the spiral, away from water, while the sugar and phosphate molecules stay on the outside. But if the bases just stack themselves, this will still leave space between the bases through which water can sneak in (see 1). This space needs to be covered up.

What are the 3 main features of DNA? ›

Each DNA strand is composed of nucleotides—units made up of a sugar (deoxyribose), a phosphate group, and a nitrogenous base. Each strand of DNA is a polynucleotide composed of units called nucleotides. A nucleotide has three components: a sugar molecule, a phosphate group, and a nitrogenous base.

What are 2 features that describe the structure of DNA *? ›

What is the structure of DNA? DNA is a double helical structure composed of nucleotides. The two helices are joined together by hydrogen bonds. The DNA also bears a sugar-phosphate backbone.

How does the discovery of DNA help us today? ›

Aside from its medical uses, the fact that DNA is unique to each individual makes it a vital forensic tool identifying criminals, the remains of a missing person, and determining the biological parent of a child. Within agriculture DNA is also used to help improve animal livestock and plants.

How did the discovery of DNA impact society? ›

Thanks to the discovery of DNA, it is now possible for scientists to identify not just the genes, but the individual bases. Before the discovery of DNA, scientists could only uncover the evolutionary tree of life by comparing the bodies and cells of different species.

Do all humans have the same DNA? ›

The human genome is mostly the same in all people. But there are variations across the genome. This genetic variation accounts for about 0.001 percent of each person's DNA and contributes to differences in appearance and health.

Why were scientists so hesitant to accept that DNA was the genetic material? ›

Scientists initially thought that DNA was too simple a molecule to be able to carry genetic information.

Does your DNA change as you age? ›

Our DNA changes as we age. Some of these changes are epigenetic—they modify DNA without altering the genetic sequence itself. Epigenetic changes affect how genes are turned on and off, or expressed, and thus help regulate how cells in different parts of the body use the same genetic code.

What type of twins are genetically identical? ›

Monozygotic (MZ) twins, also called identical twins, occur when a single egg cell is fertilized by a single sperm cell. The resulting zygote splits into two very early in development, leading to the formation of two separate embryos. MZ twins occur in 3 to 4 per 1,000 births worldwide.

Can DNA be corrupted? ›

DNA can be damaged via environmental factors as well. Environmental agents such as UV light, ionizing radiation, and genotoxic chemicals. Replication forks can be stalled due to damaged DNA and double strand breaks are also a form of DNA damage.

What happens if a mistake happens during DNA replication? ›

Extremely inaccurate DNA replication can lead to a rapid accumulation of mutations that disrupts cellular processes needed for viability and extinguish clonal populations of cells within several generations [3,4].

What happens if one mistake is made during DNA replication? ›

If DNA replication goes wrong, the cell can either repair the mistakes or go through apoptosis. During DNA replication, DNA polymerase occasionally makes errors in inserting nucleotides into the growing strand. This can be corrected by DNA polymerase itself or other DNA repair enzymes.

How often is there a mistake in DNA replication? ›

In fact, most cells have continuously purified the replication process, making errors at rates less than one base change per genetic division. For humans, this means an average of less than one error per billion bases replicated.

Did Watson and Crick steal Photo 51? ›

Gosling, working under Franklin's supervision, actually took the famous Photograph 51, whose X-shaped image would lead James Watson and Francis Crick to conceptualize DNA's structure as a double helix, the breakthrough that would lead to today's genetic treatments. But Franklin didn't show Photograph 51 to Watson.

Who is the mother of DNA? ›

Rosalind Franklin
EducationSt Paul's Girls' School
Alma materUniversity of Cambridge (PhD)
Known forStructure of DNA Fine structure of coal and graphite Structures of viruses
Scientific career
9 more rows

What shape is DNA? ›

Nucleotides are arranged in two long strands that form a spiral called a double helix. The structure of the double helix is somewhat like a ladder, with the base pairs forming the ladder's rungs and the sugar and phosphate molecules forming the vertical sidepieces of the ladder.

What 3 concepts have learned about mutation? ›

There are three types of DNA Mutations: base substitutions, deletions and insertions. Single base substitutions are called point mutations, recall the point mutation Glu -----> Val which causes sickle-cell disease.

Which form of DNA is described by Watson Crick model? ›

Watson and Crick described double helical model for secondary structure of B-form of DNA which is physiologically most important form of DNA.

What are the 4 mechanisms of mutations? ›

There are four possible results from a mutation: missense, nonsense, sense, or frameshift.

Why is it called Photo 51? ›

The play is named after one particular photograph that showed its helical structure with striking clarity, which inspired James Watson and Francis Crick to build their double helix model.

Who was the reason we now know DNA is a double helix? ›

These four scientists—Crick, Franklin, Watson, and Wilkins—codiscovered the double-helix structure of DNA, which formed the basis for modern biotechnology.

Who took Photo 51? ›

On 6 May 1952, at King´s College London in London, England, Rosalind Franklin photographed her fifty-first X-ray diffraction pattern of deoxyribosenucleic acid, or DNA.

What did Wilkins mistakenly and incorrectly think Franklin had been hired to do at Kings College London? ›

Meanwhile, Wilkins and Rosalind Franklin, researching DNA at Kings, did not function as a team; far from it. Franklin had been hired as a full-fledged, independent research scientist, but Maurice Wilkins refused to recognize her as such, and repeatedly tried to use her as his assistant. What is this?

Which important discoveries was made by Watson and Crick in the 1950s group of answer choices? ›

In the early 1950s, American biologist James Watson and British physicist Francis Crick came up with their famous model of the DNA double helix.

What did Watson and Crick not discover? ›

Watson and Crick seem never to have told Franklin directly what they subsequently have said from public platforms long after her death — that they could not have discovered the double helix of DNA in the early months of 1953 without her work.

What was unique about Watson and Crick's experiment? ›

Watson and Crick showed that each strand of the DNA molecule was a template for the other. During cell division the two strands separate and on each strand a new "other half" is built, just like the one before.

Did Rosalind Franklin face sexism? ›

Although she never complained, Franklin dealt with her fair share of discrimination and sexism. As a woman, and as a Jew, she often felt isolated from her colleagues, and these were challenges she was never quite able to overcome.

Why couldn t Franklin defend herself? ›

Worse still, Franklin had died of ovarian cancer several years earlier, and so was not able to defend herself.

What did Watson and Crick discover why was this discovery important? ›

On February 28, 1953, Cambridge University scientists James D. Watson and Francis H.C. Crick announce that they have determined the double-helix structure of DNA, the molecule containing human genes.

How does the work of Watson and Crick with DNA affect the field of evolution? ›

Thanks to the discovery of DNA, it is now possible for scientists to identify not just the genes, but the individual bases. Before the discovery of DNA, scientists could only uncover the evolutionary tree of life by comparing the bodies and cells of different species.

Who named DNA? ›

Albrecht Kossel isolated the five nucleotide bases that are the building blocks of DNA and RNA: adenine, cytosine, guanine, thymine and uracil. In 1881 Albrecht identified nuclein as a nucleic acid and provided its present chemical name, deoxyribonucleic acid (DNA).

Who stole photo 51? ›

Photo 51 is an X-ray based fiber diffraction image of a paracrystalline gel composed of DNA fiber taken by Raymond Gosling, a graduate student working under the supervision of Rosalind Franklin in May 1952 at King's College London, while working in Sir John Randall's group.

Why was the discovery of DNA so important? ›

Understanding the structure and function of DNA has helped revolutionise the investigation of disease pathways, assess an individual's genetic susceptibility to specific diseases, diagnose genetic disorders, and formulate new drugs. It is also critical to the identification of pathogens.

What is Watson and Crick's model explain with structure? ›

Watson-Crick Structure of DNA. The Watson-Crick Model of DNA (1953) Deoxyribonucleic Acid (DNA) is a double-stranded, helical molecule. It consists of two sugar-phosphate backbones on the outside, held together by hydrogen bonds between pairs of nitrogenous bases on the inside.


1. Watson and Crick model of DNA
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3. DNA double helix: how James Watson and Francis Crick cracked the secret of life
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4. Lecture 01, concept 06: Watson-Crick base pairing
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5. How I discovered DNA - James Watson
6. Rosalind Franklin vs. Watson & Crick - Science History Rap Battle
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