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How reliable are genetic ancestry tests?

How reliable are genetic ancestry tests/genealogical DNA testing?

Ancestry report 23andme family

Sample report from 23AndMe


What is the technology?


Why would people want to do this?

Learn about family history

Learn about susceptibility to diseases (Parkinson’s, Cancer)

Predicting Side Effects of Pharmaceuticals

Are we really of only the heritage that we think we are from?

If you’re black, DNA ancestry results can reveal an awkward truth, Splinter News, 2016

What companies are offering these tests?

  • 23andMe, personal genomics and biotechnology company, Mountain View, CA

  • Affymetrix

  • AncestryDNA

  • Family Tree DNA

  • MyHeritageDNA

Ethical issues


genetic counseling

Example: Tay Sachs

Five Things to Know about Direct-to-Consumer Genetic Tests. Johns Hopkins Medicine.

Alzheimer’s Society’s view on genetic testing

How reliable is the interpretation of the data?

Intro tba

How DNA Testing Botched My Family’s Heritage, and Probably Yours, Too, Gizmodo, 2018

How Accurate Are Online DNA Tests? Scientific American

Genetic tests are everywhere, but how reliable are they? Boston Globe

Pulling Back the Curtain on DNA Ancestry Tests. Tufts University

What genetic tests from 23andMe, Veritas and Genos really told me about my health. Science News

What I actually learned about my family after trying 5 DNA ancestry tests. Results Vary Wildly. Science News

Articles from scientific journals

False-positive results released by direct-to-consumer genetic tests highlight the importance of clinical confirmation testing for appropriate patient care. Nature, 2018

How is genetic testing evaluated? A systematic review of the literature. European Journal of Human Genetics, 2018

Why is the interpretation of the data often wrong?

The accuracy of the interpretations will get better over time. But for now they are not great. Why not?

Kristen V. Brown writes:

Four tests, four very different answers about where my DNA comes from—including some results that contradicted family history I felt confident was fact. What gives?

There are a few different factors at play here. Genetics is inherently a comparative science: Data about your genes is determined by comparing them to the genes of other people.

As Adam Rutherford, a British geneticist and author of the excellent book “A Brief History of Everyone Who Ever Lived,” explained to me, we’ve got a fundamental misunderstanding of what an ancestry DNA test even does.

“They’re not telling you where your DNA comes from in the past,” he told me, “They’re telling you where on Earth your DNA is from today.”

Ancestry, for example, had determined that my Aunt Cat was 30 percent Italian by comparing her genes to other people in its database of more than six million people, and finding presumably that her genes had a lot of things in common with the present-day people of Italy.

Heritage DNA tests are more accurate for some groups of people than others, depending how many people with similar DNA to yours have already taken their test. Ancestry and 23andMe have actually both published papers about how their statistical modeling works.

As Ancestry puts it: “When considering AncestryDNA estimates of genetic ethnicity it is important to remember that our estimates are, in fact, estimates. The estimates are variable and depend on the method applied, the reference panel used, and the other customer samples included during estimation.”

That the data sets are primarily made up of paying customers also skews demographics. If there’s only a small number of Middle Eastern DNA samples that your DNA has been matched against, it’s less likely you’ll get a strong Middle Eastern match.

from gizmodo How-dna-testing-botched-my-familys-heritage-and-probably yours, 2018

Further reading

Understanding genetic testing: U.S. National Library of Medicine


Learning Standards

HS-LS1-1. Construct a model of transcription and translation to explain the roles of DNA and RNA that code for proteins that regulate and carry out essential functions of life.

HS-LS3-1. Develop and use a model to show how DNA in the form of chromosomes is passed from parents to offspring through the processes of meiosis and fertilization in sexual reproduction.

HS-LS3-2. Make and defend a claim based on evidence that genetic variations (alleles) may result from (a) new genetic combinations via the processes of crossing over and random segregation of chromosomes during meiosis, (b) mutations that occur during replication, and/or (c) mutations caused by environmental factors. Recognize that mutations that occur in gametes can be passed to offspring.

HS-LS3-3. Apply concepts of probability to represent possible genotype and phenotype combinations in offspring caused by different types of Mendelian inheritance patterns.

HS-LS3-4(MA). Use scientific information to illustrate that many traits of individuals, and the presence of specific alleles in a population, are due to interactions of genetic factors
and environmental factors.



Mad science

Yup, we’re planning a lesson on real-life mad scientists and their actually-plausible mad science inventions. Because of course.

Mad Science

Nikola Tesla

Tesla and wireless power transmission


Project Habbakuk

Project Habbakuk: Britain’s secret attempt to build an ice warship. CNN.

Project Habbakuk: Britain’s Secret Ice “Bergship” Aircraft Carrier Project. 99percentinvisible.org

Project Habakkuk (Wikipedia)

Project Orion

Our SpaceFlight Heritage: Project Orion, a nuclear bomb and rocket – all in one.

Project Orion

Realistic Designs: Atomic Rockets

Project Orion. Medium.com

Extreme Engineering

Extreme Engineering: Tokyo’s Sky City, Transatlantic Tunnel, and the Space Elevator


The Mad Genius Mystery, Alexander Grothendieck

Learning Standards

2016 Massachusetts Science and Technology/Engineering Curriculum Framework

2016 High School Technology/Engineering

HS-ETS1-1. Analyze a major global challenge to specify a design problem that can be improved. Determine necessary qualitative and quantitative criteria and constraints for solutions, including any requirements set by society.

HS-ETS1-2. Break a complex real-world problem into smaller, more manageable problems that each can be solved using scientific and engineering principles.

HS-ETS1-3. Evaluate a solution to a complex real-world problem based on prioritized criteria and trade-offs that account for a range of constraints, including cost, safety, reliability, aesthetics, and maintenance, as well as social, cultural, and environmental impacts.

HS-ETS1-5(MA). Plan a prototype or design solution using orthographic projections and isometric drawings, using proper scales and proportions.

Next Generation Science Standards: Science & Engineering Practices

● Ask questions that arise from careful observation of phenomena, or unexpected results, to clarify and/or seek additional information.
● Ask questions that arise from examining models or a theory, to clarify and/or seek additional information and relationships.
● Ask questions to clarify and refine a model, an explanation, or an engineering problem.
● Evaluate a question to determine if it is testable and relevant.
● Ask and/or evaluate questions that challenge the premise(s) of an argument, the interpretation of a data set, or the suitability of the design

Francis Cabot Lowell and the industrial revolution

Before the 1760s, textile production was a cottage industry using mainly flax and wool. A typical weaving family would own one hand loom, which would be operated by the man with help of a boy; the wife, girls and other women could make sufficient yarn for that loom.

The knowledge of textile production had existed for centuries. India had a textile industry that used cotton, from which it manufactured cotton textiles. When raw cotton was exported to Europe it could be used to make fustian.

Two systems had developed for spinning: the simple wheel, which used an intermittent process and the more refined, Saxony wheel which drove a differential spindle and flyer with a heck that guided the thread onto the bobbin, as a continuous process. This was satisfactory for use on hand looms, but neither of these wheels could produce enough thread for the looms after the invention by John Kay in 1734 of the flying shuttle, which made the loom twice as productive.

Cloth production moved away from the cottage into manufactories. The first moves towards manufactories called mills were made in the spinning sector. The move in the weaving sector was later. By the 1820s, all cotton, wool and worsted was spun in mills; but this yarn went to outworking weavers who continued to work in their own homes. A mill that specialised in weaving fabric was called a weaving shed.


This section has been adapted from, Textile manufacture during the British Industrial Revolution, Wikipedia

Francis Cabot Lowell

Samuel Slater had established factories in the 1790s after building textile machinery. Francis Cabot Lowell took it a step further. In 1810, Francis Cabot Lowell visited the textile mills in England. He took note of the machinery in England that was not available in the United States, and he sketched and memorized details.

Francis Cabot Lowell from Hulton Archive, Getty Images

One machine in particular, the power loom, could weave thread into cloth. He took his ideas to the United States and formed the Boston Manufacturing Company in 1812. With the money he made from this company, he built a water-powered mill. Francis Cabot Lowell is credited for building the first factory where raw cotton could be made into cloth under one roof. This process, also known as the “Waltham-Lowell System” reduced the cost of cotton. By putting out cheaper cotton, Lowell’s company quickly became successful. After Lowell brought the power loom to the United States, the new textile industry boomed. The majority of businesses in the United States by 1832 were in the textile industry.

Lowell also found a specific workforce for his textile mills. He employed single girls, daughters of New England farm families, also known as The Lowell Girls. Many women were eager to work to show their independence. Lowell found this convenient because he could pay women less wages than he would have to pay men. Women also worked more efficiently than men did, and were more skilled when it came to cotton production. This way, he got his work done efficiently, with the best results, and it cost him less. The success of the Lowell mills symbolizes the success and technological advancement of the Industrial Revolution.

– This has been excerpted from https://firstindustrialrevolution.weebly.com/the-textile-industry.html

Learning Standards

Massachusetts Science and Technology/Engineering Curriculum Framework

HS-ETS4-5(MA). Explain how a machine converts energy, through mechanical means, to do work. Collect and analyze data to determine the efficiency of simple and complex machines.

Massachusetts History and Social Science Curriculum Framework

Grade 6: HISTORY AND GEOGRAPHY Interpret geographic information from a graph or chart and construct a graph or chart that conveys geographic information (e.g., about rainfall, temperature, or population size data)

INDUSTRIAL REVOLUTION AND SOCIAL AND POLITICAL CHANGE IN EUROPE, 1800–1914 WHII.6 Summarize the social and economic impact of the Industrial Revolution… population and urban growth

Benchmarks, American Association for the Advancement of Science

In the 1700s, most manufacturing was still done in homes or small shops, using small, handmade machines that were powered by muscle, wind, or moving water. 10J/E1** (BSL)

In the 1800s, new machinery and steam engines to drive them made it possible to manufacture goods in factories, using fuels as a source of energy. In the factory system, workers, materials, and energy could be brought together efficiently. 10J/M1*

The invention of the steam engine was at the center of the Industrial Revolution. It converted the chemical energy stored in wood and coal into motion energy. The steam engine was widely used to solve the urgent problem of pumping water out of coal mines. As improved by James Watt, Scottish inventor and mechanical engineer, it was soon used to move coal; drive manufacturing machinery; and power locomotives, ships, and even the first automobiles. 10J/M2*

The Industrial Revolution developed in Great Britain because that country made practical use of science, had access by sea to world resources and markets, and had people who were willing to work in factories. 10J/H1*

The Industrial Revolution increased the productivity of each worker, but it also increased child labor and unhealthy working conditions, and it gradually destroyed the craft tradition. The economic imbalances of the Industrial Revolution led to a growing conflict between factory owners and workers and contributed to the main political ideologies of the 20th century. 10J/H2

Today, changes in technology continue to affect patterns of work and bring with them economic and social consequences. 10J/H3*

The Enlightenment

Notes for teachers who are covering the age of the Enlightenment

A Reading in the Salon of Mme Geoffrin by Anicet Lemonnier

“A Reading in the Salon of Mme Geoffrin,” 1755, By Anicet Charles Gabriel Lemonnier. Marie Geoffrin was one of the leading female figures in the French Enlightenment. She hosted some of the most important Philosophes and Encyclopédistes of her time.


For now, this introduction has been loosely adapted from the Wikipedia article.

French historians traditionally place the Enlightenment between 1715 (the year that Louis XIV died) and 1789 (the beginning of the French Revolution).

International historians often say that the Enlightenment began in the 1620s, with the start of the scientific revolution.

Earlier philosophers whose work influenced the Enlightenment included Bacon, Descartes, Locke, and Spinoza.

Many of the Enlightenment thinkers are known as Les philosophes -French writers and thinkers – who – circulated their ideas through meetings at scientific academies, Masonic lodges, literary salons, coffee houses, and in printed books and pamphlets.

The ideas of the Enlightenment undermined the authority of the monarchy and the Church. These ideas paved the way for the political revolutions of the 18th and 19th centuries.

Major figures of the Enlightenment included Beccaria, Diderot, Hume, Kant, Montesquieu, Rousseau, Adam Smith, and Voltaire.

Some European rulers, including Catherine II of Russia, Joseph II of Austria and Frederick II of Prussia, tried to apply Enlightenment thought on religious and political tolerance, “enlightened absolutism.”

Benjamin Franklin visited Europe and contributed to the scientific and political debates there; he brought these ideas back to Philadelphia. Thomas Jefferson incorporated Enlightenment philosophy into the Declaration of Independence (1776). James Madison, incorporated these ideas in the United States Constitution during its framing in 1787

Secondary section (to be re-titled)

In his famous 1784 essay “What Is Enlightenment?”, Immanuel Kant defined it as follows:

“Enlightenment is man’s leaving his self-caused immaturity. Immaturity is the incapacity to use one’s own understanding without the guidance of another. Such immaturity is self-caused if its cause is not lack of intelligence, but by lack of determination and courage to use one’s intelligence without being guided by another. The motto of enlightenment is therefore: Have courage to use your own intelligence!”

By mid-Century the pinnacle of purely Enlightenment thinking was being reached with Voltaire.

Born Francois Marie Arouet in 1694, he was exiled to England between 1726 and 1729, and there he studied Locke, Newton, and the English Monarchy.

Voltaire’s ethos was:  “Those who can make you believe absurdities can make you commit atrocities” – that is, if people believed in what is unreasonable, they will do what is unreasonable.

Reforms sought

The Enlightenment sought reform of Monarchy by laws which were in the best interest of the subjects, and the “enlightened” ordering of society.  In the 1750s there would be attempts in England, Austria, Prussia and France to “rationalize” the Monarchical system and its laws. When this failed to end wars, there was an increasing drive for revolution or dramatic alteration. The Enlightenment found its way to the heart of the American Declaration of Independence, and the Jacobin program of the French Revolution, as well as the American Constitution of 1787.

Common values

Many values were common to enlightenment thinkers, including:

✔ Nations exist to protect the rights of the individual, instead of the other way around.

✔ Each individual should be afforded dignity, and should be allowed to live one’s life with the maximum amount of personal freedom.

✔ Some form of Democracy is the best form of government.

✔ All of humanity, all races, nationalities and religions, are of equal worth and value.

✔ People have a right to free speech and expression, the right to free association, the right to hold to any – or no – religion; the right to elect their own leaders.

✔ The scientific method is our only ally in helping us discern fact from fiction.

✔Science, properly used, is a positive force for the good of all humanity.

✔ Classical religious dogma and mystical experiences are inferior to logic and philosophy.

✔ Theism – the belief in a God that wants morality – was held by most Enlightenment thinkers to be essential for a person to have good moral character. 

✔ Deism – to be added

✔ Some classical religious dogma has been harmful, causing crusades, Jihads, holy wars, or denial of human rights to various classes of people.

Learning Standards

Massachusetts History and Social Science Curriculum Framework

High School World History Content Standards

Topic 6: Philosophies of government and society Supporting question: How did philosophies of government shape the everyday lives of people? 34. Identify the origins and the ideals of the European Enlightenment, such as happiness, reason, progress, liberty, and natural rights, and how intellectuals of the movement (e.g., Denis Diderot, Emmanuel Kant, John Locke, Charles de Montesquieu, Jean-Jacques Rousseau, Mary Wollstonecraft, Cesare Beccaria, Voltaire, or social satirists such as Molière and William Hogarth) exemplified these ideals in their work and challenged existing political, economic, social, and religious structures.

New York State Grades 9-12 Social Studies Framework


9.9d The development of the Scientific Revolution challenged traditional authorities and beliefs.  Students will examine the Scientific Revolution, including the influence of Galileo and Newton.
9.9e The Enlightenment challenged views of political authority and how power and authority were conceptualized.

10.2: ENLIGHTENMENT, REVOLUTION, AND NATIONALISM: The Enlightenment called into question traditional beliefs and inspired widespread political, economic, and social change. This intellectual movement was used to challenge political authorities in Europe and colonial rule in the Americas. These ideals inspired political and social movements.

10.2a Enlightenment thinkers developed political philosophies based on natural laws, which included the concepts of social contract, consent of the governed, and the rights of citizens.

10.2b Individuals used Enlightenment ideals to challenge traditional beliefs and secure people’s rights in reform movements, such as women’s rights and abolition; some leaders may be considered enlightened despots.

10.2c Individuals and groups drew upon principles of the Enlightenment to spread rebellions and call for revolutions in France and the Americas.

History–Social Science Content Standards for California Public Schools

7.11 Students analyze political and economic change in the sixteenth, seventeenth, and eighteenth centuries (the Age of Exploration, the Enlightenment, and the Age of Reason).
1. Know the great voyages of discovery, the locations of the routes, and the influence of cartography in the development of a new European worldview.
2. Discuss the exchanges of plants, animals, technology, culture, and ideas among Europe, Africa, Asia, and the Americas in the fifteenth and sixteenth centuries and the
major economic and social effects on each continent.
3. Examine the origins of modern capitalism; the influence of mercantilism and cottage industry; the elements and importance of a market economy in seventeenth-century Europe; the changing international trading and marketing patterns, including their locations on a world map; and the influence of explorers and map makers.
4. Explain how the main ideas of the Enlightenment can be traced back to such movements as the Renaissance, the Reformation, and the Scientific Revolution and to the Greeks, Romans, and Christianity.
5. Describe how democratic thought and institutions were influenced by Enlightenment thinkers (e.g., John Locke, Charles-Louis Montesquieu, American founders).
6. Discuss how the principles in the Magna Carta were embodied in such documents as the English Bill of Rights and the American Declaration of Independence.

AP World History

The 18th century marked the beginning of an intense period of revolution and rebellion against existing governments, and the establishment of new nation-states around the world.

I. The rise and diffusion of Enlightenment thought that questioned established traditions in all areas of life often preceded the revolutions and rebellions against existing governments.

Also see AP Worldipedia. Key Concept 5.3 Nationalism, Revolution, and Reform

Speculative history: Possibility of prehuman civilization

Could an intelligent species have lived on Earth before humanity? Could it even have developed an industrial civilization? If one had existed on Earth – many millions of years prior to our own era – what traces would it have left and would they be detectable today?

The Stairway of Time Geologic eras

Technosignatures of pre-human civilizations here on Earth


Did Antarctica remain entirely unvisited by humans until the early 19th century? History.Stackexchange.Com

Could an Industrial Prehuman Civilization Have Existed on Earth before Ours? Scientific American

Was There a Civilization On Earth Before Humans? A look at the available evidence. The Atlantic.

Technosignatures of ET life elsewhere in our solar system

THE BIG QUESTIONS Did Intelligent Space Aliens Once Live in Our Solar System? NBC News

The Silurian Hypothesis: Would it be possible to detect an industrial civilization in the geological record? Gavin A. Schmidt, Adam Frank

If an industrial civilization had existed on Earth many millions of years prior to our own era, what traces would it have left and would they be detectable today? We summarize the likely geological fingerprint of the Anthropocene, and demonstrate that while clear, it will not differ greatly in many respects from other known events in the geological record. We then propose tests that could plausibly distinguish an industrial cause from an otherwise naturally occurring climate event.

Prior Indigenous Technological Species, Jason T. Wright

One of the primary open questions of astrobiology is whether there is extant or extinct life elsewhere the Solar System. Implicit in much of this work is that we are looking for microbial or, at best, unintelligent life, even though technological artifacts might be much easier to find. SETI work on searches for alien artifacts in the Solar System typically presumes that such artifacts would be of extrasolar origin, even though life is known to have existed in the Solar System, on Earth, for eons.

But if a prior technological, perhaps spacefaring, species ever arose in the Solar System, it might have produced artifacts or other technosignatures that have survived to present day, meaning Solar System artifact SETI provides a potential path to resolving astrobiology’s question.

Here, I discuss the origins and possible locations for technosignatures of such a prior indigenous technological species, which might have arisen on ancient Earth or another body, such as a pre-greenhouse Venus or a wet Mars. In the case of Venus, the arrival of its global greenhouse and potential resurfacing might have erased all evidence of its existence on the Venusian surface. In the case of Earth, erosion and, ultimately, plate tectonics may have erased most such evidence if the species lived Gyr ago. Remaining indigenous technosignatures might be expected to be extremely old, limiting the places they might still be found to beneath the surfaces of Mars and the Moon, or in the outer Solar System.

Zombie based geography

I want to share these ideas with other educators and with students.


Zombie-Based Learning (ZBL) is the brainchild of David Hunter, former teacher from the Bellevue Big Picture school, in a suburb of Seattle, Washington.  It uses Project-Based Learning to encourage active engagement, problem solving and critical thinking skills.

Student Zombie Map

Student photo made available from Zombie-Based Learning (ZBL),

When the zombies attack, where should we run, where regroup, and where rebuild our lives? Those questions, key to survival, can focus student attention on a highly motivating and dangerously overlooked fact: Geography skills can save you from the zombie apocalypse!

Use students’ natural desire to survive zombie assaults to motivate study of a complete curriculum based on the 2012 National Geography Standards, and then to apply those skills in a series of scenarios based on surviving when the attacks come to your own neighborhood.



Making History is Project-Based Learning curriculum created by award-winning teacher David Hunter, designed for standards-based classrooms. Launched on Kickstarter, it’s nine units with projects for middle school students. Teach cross-content or by individual subject, with a time travel backstory to drive students’ interest and engagement. The narrative follows a group of entrepreneurial and altruistic students who go back in time, and work together to invent or discover critical breakthroughs BEFORE they occur in our true historical timeline.



Zombies worksheet

Did Watson and Crick really steal Rosalind Franklin’s data?

Sexism in science: did Watson and Crick really steal Rosalind Franklin’s data?

The race to uncover the structure of DNA reveals fascinating insights into how Franklin’s data was key to the double helix model, but the ‘stealing’ myth stems from Watson’s memoir and attitude rather than facts.

Photo 51 DNA Diffraction pattern

X-ray diffraction image of the double helix structure of the DNA molecule, taken 1952 by Raymond Gosling, commonly referred to as “Photo 51”, during work by Rosalind Franklin on the structure of DNA (text Wikipedia)

Matthew Cobb, The Guardian, 6/23/15

The wave of protest that followed Sir Tim Hunt’s stupid comments about ‘girls’ in laboratories highlighted many examples of sexism in science. One claim was that during the race to uncover the structure of DNA, Jim Watson and Francis Crick either stole Rosalind Franklin’s data, or ‘forgot’ to credit her. Neither suggestion is true.

In April 1953, the scientific journal Nature published three back-to-back articles on the structure of DNA, the material our genes are made of. Together, they constituted one of the most important scientific discoveries in history.

The first, purely theoretical, article was written by Watson and Crick from the University of Cambridge. Immediately following this article were two data-rich papers by researchers from King’s College London: one by Maurice Wilkins and two colleagues, the other by Franklin and a PhD student, Ray Gosling.

Rosalind Franklin

Credit: Vittoria Luzzati/NPG

The model the Cambridge duo put forward did not simply describe the DNA molecule as a double helix. It was extremely precise, based on complex measurements of the angles formed by different chemical bonds, underpinned by some extremely powerful mathematics and based on interpretations that Crick had recently developed as part of his PhD thesis. The historical whodunnit, and the claims of data theft, turn on the origin of those measurements.

The four protagonists would make good characters in a novel – Watson was young, brash, and obsessed with finding the structure of DNA; Crick was brilliant with a magpie mind, and had struck up a friendship with Wilkins, who was shy and diffident. Franklin, an expert in X-ray crystallography, had been recruited to King’s in late 1950. Wilkins expected she would work with him, but the head of the King’s group, John Randall, led her to believe she would be independent.

From the outset, Franklin and Wilkins simply did not get on. Wilkins was quiet and hated arguments; Franklin was forceful and thrived on intellectual debate. Her friend Norma Sutherland recalled: “Her manner was brusque and at times confrontational – she aroused quite a lot of hostility among the people she talked to, and she seemed quite insensitive to this.”

Watson and Crick’s first foray into trying to crack the structure of DNA took place in 1952. It was a disaster. Their three-stranded, inside-out model was hopelessly wrong and was dismissed at a glance by Franklin. Following complaints from the King’s group that Watson and Crick were treading on their toes, Sir Lawrence Bragg, the head of their lab in Cambridge told them to cease all work on DNA.

However, at the beginning of 1953, a US competitor, Linus Pauling, became interested in the structure of DNA, so Bragg decided to set Watson and Crick on the problem once more.

At the end of January 1953, Watson visited King’s, where Wilkins showed him an X-ray photo that was subsequently used in Franklin’s Nature article. This image, often called ‘Photo 51’, had been made by Raymond Gosling, a PhD student who had originally worked with Wilkins, had then been transferred to Franklin (without Wilkins knowing), and was now once more being supervised by Wilkins, as Franklin prepared to leave the terrible atmosphere at King’s and abandon her work on DNA.

Watson recalled that when he saw the photo – which was far clearer than any other he had seen – ‘my mouth fell open and my pulse began to race.’ According to Watson, photo 51 provided the vital clue to the double helix. But despite the excitement that Watson felt, all the main issues, such as the number of strands and above all the precise chemical organisation of the molecule, remained a mystery. A glance at photo 51 could not shed any light on those details.

What Watson and Crick needed was far more than the idea of a helix – they needed precise observations from X-ray crystallography. Those numbers were unwittingly provided by Franklin herself, included in a brief informal report that was given to Max Perutz of Cambridge University.

In February 1953, Perutz passed the report to Bragg, and thence to Watson and Crick.

Crick now had the material he needed to do his calculations. Those numbers, which included the relative distances of the repetitive elements in the DNA molecule, and the dimensions of what is called the monoclinic unit cell – which indicated that the molecule was in two matching parts, running in opposite directions – were decisive.

The report was not confidential, and there is no question that the Cambridge duo acquired the data dishonestly. However, they did not tell anyone at King’s what they were doing, and they did not ask Franklin for permission to interpret her data (something she was particularly prickly about).

Their behaviour was cavalier, to say the least, but there is no evidence that it was driven by sexist disdain: Perutz, Bragg, Watson and Crick would have undoubtedly behaved the same way had the data been produced by Maurice Wilkins.

Ironically, the data provided by Franklin to the MRC were virtually identical to those she presented at a small seminar in King’s in autumn 1951, when Jim Watson was in the audience. Had Watson bothered to take notes during her talk, instead of idly musing about her dress sense and her looks, he would have provided Crick with the vital numerical evidence 15 months before the breakthrough finally came.

By chance, Franklin’s data chimed completely with what Crick had been working on for months: the type of monoclinic unit cell found in DNA was also present in the horse haemoglobin he had been studying for his PhD. This meant that DNA was in two parts or chains, each matching the other. Crick’s expertise explains why he quickly realised the significance of these facts, whereas it took Franklin months to get to the same point.

While Watson and Crick were working feverishly in Cambridge, fearful that Pauling might scoop them, Franklin was finishing up her work on DNA before leaving the lab. The progress she made on her own, increasingly isolated and without the benefit of anyone to exchange ideas with, was simply remarkable.

Franklin’s laboratory notebooks reveal that she initially found it difficult to interpret the outcome of the complex mathematics – like Crick, she was working with nothing more than a slide rule and a pencil – but by 24 February, she had realised that DNA had a double helix structure and that the way the component nucleotides or bases on each strand were connected meant that the two strands were complementary, enabling the molecule to replicate.

Above all, Franklin noted that ‘an infinite variety of nucleotide sequences would be possible to explain the biological specificity of DNA’, thereby showing that she had glimpsed the most decisive secret of DNA: the sequence of bases contains the genetic code.

To prove her point, she would have to convert this insight into a precise, mathematically and chemically rigorous model. She did not get the chance to do this, because Watson and Crick had already crossed the finishing line – the Cambridge duo had rapidly interpreted the double helix structure in terms of precise spatial relationships and chemical bonds, through the construction of a physical model.

In the middle of March 1953, Wilkins and Franklin were invited to Cambridge to see the model, and they immediately agreed it must be right. It was agreed that the model would be published solely as the work of Watson and Crick, while the supporting data would be published by Wilkins and Franklin – separately, of course. On 25 April there was a party at King’s to celebrate the publication of the three articles in Nature. Franklin did not attend. She was now at Birkbeck and had stopped working on DNA.

Franklin died of ovarian cancer in 1958, four years before the Nobel prize was awarded to Watson, Crick and Wilkins for their work on DNA structure. She never learned the full extent to which Watson and Crick had relied on her data to make their model; if she suspected, she did not express any bitterness or frustration, and in subsequent years she became very friendly with Crick and his wife, Odile.

Our picture of how the structure of DNA was discovered, and the myth about Watson and Crick stealing Franklin’s data, is almost entirely framed by Jim Watson’s powerful and influential memoir, The Double Helix. Watson included frank descriptions of his own appalling attitude towards Franklin, whom he tended to dismiss, even down to calling her ‘Rosy’ in the pages of his book – a nickname she never used (her name was pronounced ‘Ros-lind’). The epilogue to the book, which is often overlooked in criticism of Watson’s attitude to Franklin, contains a generous and fair description by Watson of Franklin’s vital contribution and a recognition of his own failures with respect to her – including using her proper name.

It is clear that, had Franklin lived, the Nobel prize committee ought to have awarded her a Nobel prize, too – her conceptual understanding of the structure of the DNA molecule and its significance was on a par with that of Watson and Crick, while her crystallographic data were as good as, if not better, than those of Wilkins. The simple expedient would have been to award Watson and Crick the prize for Physiology or Medicine, while Franklin and Watkins received the prize for Chemistry.

Whether the committee would have been able to recognise Franklin’s contribution is another matter. As the Tim Hunt affair showed, sexist attitudes are ingrained in science, as in the rest of our culture.

By Matthew Cobb


This website is educational. Materials within it are being used in accord with the Fair Use doctrine, as defined by United States law.

§107. Limitations on Exclusive Rights: Fair Use. Notwithstanding the provisions of section 106, the fair use of a copyrighted work, including such use by reproduction in copies or phone records or by any other means specified by that section, for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an infringement of copyright. In determining whether the use made of a work in any particular case is a fair use, the factors to be considered shall include: the purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes; the nature of the copyrighted work; the amount and substantiality of the portion used in relation to the copyrighted work as a whole; and the effect of the use upon the potential market for or value of the copyrighted work. (added pub. l 94-553, Title I, 101, Oct 19, 1976, 90 Stat 2546)