Rosalind Franklin: The Unsung Hero of DNA Structure

Rosalind Franklin, a scientist whose role in the discovery of DNA structure in 1953 has been forgotten by many, has a chance to be immortalized in a feature film. Throughout her career she faced sexism at nearly every turn. She also happened to be Jewish, which heightened the prejudice against her. Her name may soon be on the tips of everyone’s tongue and her role in the discovery of DNA Structure known to all. Entertainment One has acquired the script to Exposure, her life story.

In 1962 James Watson, Francis Crick, and Maurice Wilkins jointly received the Nobel Prize in physiology or medicine for their 1953 determination of the structure of deoxyribonucleic acid (DNA). Rosalind Franklin (1920–1958), a colleague of Wilkins, died of cancer at the age of 37, and was thereby not equally honored because the Nobel Prize can only be shared by three scientists. It was her work in X-ray crystallography, however, that proved critical to the correct solution to DNA structure.

Unsung Hero of DNA Structure @EvaVarga.netWhat is DNA?  

DNA is the material embedded in the cells of all living organisms that carries the genetic coding that determines how a living thing will look and function. It is found in the nucleus of each cell and is unique to every individual – whether human, mountain lion, or butterfly. Its full name is deoxyribonucleic acid, which can be complicated to say, so we usually refer to it as DNA for short.

DNA is so tiny that it can not be seen unless we use a very powerful microscope. If we could see it we would see that it looks like a twisted ladder, which scientist refer to as the double helix. Each rung or step on the DNA ladder is composed of two letters.

There are only 4 letters — A,T,G, and C — and each has a unique puzzle-like shape. This means that A and T fit together to form a rung on the ladder and G and C fit together to form another rung on the ladder.

As we read the DNA ladder, the letters combine to form 3-letter words called codons. Then, these codons combine to form sentences that we call genes. These genes are the basis for your chromosomes, which give your body a blueprint or set of instructions for life.

Every human has 23 pairs of these DNA chromosomes that determine what we look like and how to perform. We get one set of chromosomes from our mother and one set from our father. Our chromosomes determine whether our eyes will be blue or brown, what color our skin and hair will be, whether we will be a boy or girl and so much more.

The Structure of DNA @EvaVarga.net

Building a Cardboard Safari DNA Double Helix Puzzle

Discovering DNA Structure

Inspired by Linus Pauling’s success in working with molecular models, James Watson and Francis Crick rapidly put together several models of DNA and attempted to incorporate all the evidence they could gather. Franklin’s excellent X-ray photographs, to which they had gained access without her permission, were critical to the correct solution. Along with Wilkins, Franklin’s partner, the four scientists announced the structure of DNA in articles that appeared together in the same issue of Nature.

After the publication, they moved on to different projects. Franklin went to Birkbeck College, London. Before her untimely death from cancer, she made important contributions to the X-ray crystallographic analysis of the structure of the tobacco mosaic virus, a landmark in the field. By the end of her life, she had become friends with Francis Crick and his wife and had moved her laboratory to Cambridge, where she undertook work on the poliovirus.

Biography

Rosalind Franklin @EvaVarga.netRosalind Franklin was born July 25, 1920 to a Jewish family in London, England. Educated at private schools in London, she studied natural sciences at Newnham College, Cambridge, from where she graduated in 1941. She joined the University of Cambridge where she earned a research fellowship in a physical chemistry laboratory under Ronald George Wreyford Norrish. The British Coal Utilisation Research Association offered her a research position in 1942, and started her work on coals. This helped her earn a PhD in 1945.

In 1947, she went to Paris as a chercheur (post-doctoral researcher) under Jacques Mering at the Laboratoire Central des Services Chimiques de l’Etat, where she became an accomplished X-ray crystallographer. She returned to London in 1951 and became a research associate at King’s College. She was compelled to move to Birkbeck College after two years, however, owing to disagreeable clashes with her director and more so with her colleague Maurice Wilkins. At Birkbeck, J. D. Bernal, chair of the physics department, offered her a separate research team. She died on April 16, 1958 at the age of 37 of ovarian cancer.

Bring it Home

Build a model of the DNA Double Helix with the Cardboard Safari Puzzle

Create a model of DNA with colorful Wiki-Sticks

Extract DNA from Strawberries in this great lab from Marci at the Homeschool Scientist

Explore the DNA Teaching Resources from Karyn at Teach Beside Me

Challenge your students with this Transcription / Translation Lab Activity 

Download the DNA & RNA Protein Synthesis Interactive Notebook Resources from Science with Amy

Make these cool DNA Sequence Bracelets

Watch this fabulous NOVA documentary on PBS, The Secret of Photo 51

Science Milestones

You may also be interested in learning about other inventors and scientists who have made an impact in our lives.

The bloggers of the iHomeschool Network have teamed up to create fun and original unit studies on fascinating people who were born in July.

Unlocking the Secrets of Invisible Ink

Have You Ever Wondered …

How does invisible ink work?

What common household substances can be used to make invisible ink?

What things can you do to reveal a message written in invisible ink?

Steganography is the practice of concealing a file, message, image, or video within another. The use of invisible inks is one of the earliest known examples of steganography. Invisible ink today is mostly considered child’s play, but in the not too distant past, its use and the recipes were considered classified government information.

Using the suggested inks and reagents provided here, write a secret message to a friend. Then get creative and see how many kinds of invisible ink you can find.Unlocking the Secrets of Invisible Ink @EvaVarga.net

Types of Invisible Inks

There are two categories into which invisible inks fall ~ organic fluids and sympathetic inks. You can find many heat-activated invisible inks right inside your kitchen. Another type of invisible ink is chemically activated. Read on to learn more about each.

Organic or Heat-Activated Invisible Inks

Organic fluids consist of the natural methods your likely already familiar: lemon juice, vinegar, milk, or onion juice, to name a few. These organic invisible inks can be revealed through heat, such as with fire, irons, or light bulbs.

The organic fluids alter the fibers of the paper so that the secret writing has a lower burn temperature and turns brown faster than the surrounding paper when exposed to heat. To activate or develop the ink, simply iron the paper, set it on a radiator, place it in an oven (set lower than 450° F), or hold it up to a hot light bulb.

  • any acidic fruit juice (e.g., lemon, apple, or orange juice)
  • onion juice
  • sodium bicarbonate NaHCOsolution (baking soda)
  • vinegar
  • white wine
  • diluted cola
  • milk
  • soapy water
  • sucrose solution (table sugar)
  • bodily fluids

solution is a homogeneous mixture composed of two or more substances. In such a mixture, a solute (baking soda or sugar) is a substance dissolved in another substance, known as a solvent (water).

Inquiry Science :: What other organic inks can you find? Which kind shows up best? Which kind lasts longest?

Unlocking the Secrets of Invisible Ink @EvaVarga.net

Sympathetic Inks

Sympathetic inks contain one or more chemicals and require the application of a specific “reagent” to be activated, such as another chemical or a mixture of chemicals. Most of these inks work using pH indicators, requiring the recipient to paint or spray a suspected message with a base (like sodium carbonate Na₂CO₃ or washing soda solution) or an acid (like lemon juice). Some of these inks will reveal their message when heated.

  • lemon juice, activated by iodine solution
  • starch (e.g., corn starch or potato starch), activated by iodine solution
  • vinegar or dilute acetic acid CH3COOH, activated by red cabbage water
  • ammonia NH3, activated by red cabbage water
  • sodium bicarbonate NaHCO3 (baking soda), activated by grape juice
  • sodium chloride NaCl (table salt), activated by silver nitrate
  • phenolphthalein (pH indicator), activated by ammonia fumes or sodium carbonate Na₂CO₃ (or another base)
  • lead nitrate, activated by sodium iodide
  • iron sulfate, activated by sodium carbonate, sodium sulfide, or potassium ferricyanide

CAUTION: Some of the chemicals suggested here can be hazardous if misused. Always use caution when working with chemicals. Read the information on the chemical label before you start, and always wear protective safety equipment such as goggles, gloves, and aprons. Adult supervision required.

Ultraviolet Light Activated Invisible Inks

Most of the inks that become visible when you shine an ultraviolet or black light on them will also become visible if you heat the paper. Here are are few ‘glow-in-the-dark’ ideas to try:

  • dilute laundry detergent (the bluing agent glows)
  • tonic water (quinine glows)
  • vitamin B-12 dissolved in vinegar

The History of Invisible Ink

The history of invisible ink is incredibly fascinating and swings wildly between high-tech methods and the humblest of approaches. Invisible ink was a key method for spy communications throughout history. Prisoners, Lovers, and Spies is an historical account of invisible ink and the secret communications revealed through thrilling stories about scoundrels, heroes, and their ingenious methods for concealing messages.

The Catholic Mary, Queen of Scots, kept under luxurious house arrest for eighteen years by her Protestant cousin Elizabeth I, advised correspondents to write to her employing two commonly used substances: alum (hydrated potassium aluminum sulfate) or nutgall (the tannic acid secreted in swellings generated by parasitic wasps colonizing oak trees). Letters written in alum required the recipient to soak the paper in water, while nutgall needed a solution of ferrous sulphate as a reagent.

During World War II, chemist Linus Pauling worked on an unusual wartime project, formulating new kinds of invisible ink that would resist all known reagents. Pauling and his colleagues experimented with invisible inks made from pneumococcus bacteria (an inert strain so as not to spread pneumonia). The ink-ified microbe would react to an antibody, and then become visible once dipped in a dye solution. However, the ink never passed the experimental stage.

Visit The Art of Manliness for a more detailed look at how invisible inks have been used in espionage and naval intelligence.

Science Milestones: Linus Pauling & Molecular Medicine

As an Oregon State University alum, Linus Pauling’s memory invokes a sense of pride. Not only was he one of the greatest scientists of our modern age, but he was also a much respected and beloved defender of civil liberties and health issues.

My father, when I had just about reached my ninth birthday, wrote a letter to the Portland Oregonian, asking for advice as to what books to get for me. He said that I seemed to have an unusual interest in reading, especially history. Then he went on to say, “And don’t say the Bible and Darwin’s Origin of Species, because he has already read them.”

linuspauling

Biography

Linus Carl Pauling was born in Portland, Oregon, on February 28, 1901. He received his early education in Oregon, finishing in 1922 with a bachelor’s degree in chemical engineering from Oregon Agricultural College in Corvallis — now Oregon State University. Already he was drawn to the challenge of how and why particular atoms form bonds with each other to create molecules with unique structures.

LinusPaulingFor postgraduate study Pauling went to the California Institute of Technology (Caltech), which provided a stipend for research and teaching. In 1925 he received a Ph.D. in chemistry and mathematical physics. Awarded a Guggenheim Fellowship, in 1926-27 he studied in Europe with physicists who were exploring the implications of quantum mechanics for atomic structure. In this revolutionary new field Pauling found a physical and mathematical framework for his own future theories regarding molecular structure and its correlation with chemical properties and function.

Pauling discovered that in many cases the type of bonding — whether ionic or covalent (formed by a sharing of electrons between bonded atoms) — could be determined from a substance’s magnetic properties. To explain covalent bonding, Pauling introduced two major new concepts, based on quantum mechanics: bond-orbital hybridization and bond resonance.

Pauling originated the concept of molecular disease. In 1945, while hearing a physician describe sickle cell anemia, he instantly surmised that it might be caused by a defect in the red blood cell’s hemoglobin. After three years of painstaking research, he and his associate Dr. Harvey Itano identified this prevalent disease as molecular in origin — caused by a genetically transmitted abnormality in the hemoglobin molecule.

“I have always liked working in some scientific direction that nobody else is working in.”

Pauling’s description of this first molecular disease initiated a search for many more such disorders. The new idea quickly became immensely important in medicine and is now the main focus of human genome research. Thus the medical specialties of hematology, serology, immunology, applied genetics, and pathology owe much to Pauling’s contributions, which were made long before his intense interest in the promise of nutritional therapy became widely known.

In 1954 Linus Pauling was awarded the Nobel Prize in Chemistry. Pauling put his elevated new position as a Nobel laureate to good effect in his growing social activism. In the late 1950s and early 1960s he protested vehemently against atmospheric nuclear testing.

Pauling’s antitesting campaign was vindicated when a treaty was signed by the three nuclear powers — the U.S., Great Britain, and the U.S.S.R. On October 10, 1963, the day on which the limited test ban went into effect, it was announced that Linus Pauling would be awarded the Nobel Peace Prize for 1962.

Linus Pauling is the only person to be awarded two unshared Nobel Prizes and one of only four individuals to have won more than one Nobel Prize (the others being Marie Curie, John Bardeen, and Frederick Sanger). Also of note, he and Marie Curie are the only people to be awarded Nobel Prizes in different fields.

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