The Mandela Effect refers to a situation in which a large mass of people believes that an event occurred when it did not. Like Darth Vader does not actually say “Luke, I am your father”, it is commonly misstated that James Watson and Francis Crick ‘discovered’ DNA. They did discover the structure, sure, but the whole story is so much more complex. Let’s take a look.
Pre-structure
DNA was first identified in the 1860s by a Swiss chemist called Johann Friedrich Miescher. As with many biological discoveries, this was done by accident. Johann initially set out to discover components of white blood cells. Here, he noticed that when acid was added to a solution of white blood cells, a substance separated from the solution. This substance then redissolved on the addition of alkali. Johann named the substance nuclein, as he believed it came from the nucleus. Many additional experiments followed, and his results were not published until 1874.
Things were quiet for a time, until in 1881 Albrecht Kossel, a German biochemist, identified nuclein as a nucleic acid and provided its present chemical name, deoxyribonucleic acid. He also isolated the five nucleotide bases adenine (A), cytosine (C), guanine (G), thymine (T) and uracil (U). In 1910, Kossel was awarded the Nobel Prize in Physiology or Medicine.
Shortly after, Walther Flemming discovered chromosomes, and through observation of their movements, he subsequently deduced how chromosomes separated during mitosis.
Through the first half of the 1900s, there was a cascade of DNA discoveries including:
- 1902 — Mendel’s theories were finally associated with a human disease by Sir Archibald Edward Garrod.
- 1944 — Oswald Avery first outlined DNA as the transforming principle.
- Late 1940s — Barbara McClintock discovered the mobility of genes and was awarded the Nobel Prize in Physiology or Medicine.
- 1944-1950 — Erwin Chargaff discovered that DNA is responsible for heredity and that it varies between species. He concluded that the amounts of adenine and thymine in DNA were roughly the same, as were the amounts of cytosine and guanine. This later became known as Chargaff’s rule.
…until finally, in 1951, Rosalind Franklin started to apply her expertise in X-ray diffraction techniques to the structure of DNA.
The structure
Franklin used a new fine-focus X-ray tube and microcamera. A critical innovation she applied was making a camera chamber that could be controlled for its humidity using different saturated salt solutions.
She discovered that a DNA sample could exist in two forms: at a relative humidity higher than 75%, the DNA fibre became long and thin; when it was drier, it became short and fat. She originally referred to the former as “wet” (now known as A) and the latter as “crystalline” (now known as B).
She presented these data at a lecture in November 1951 in King’s College London. In her lecture notes, she wrote the following:
“The results suggest a helical structure (which must be very closely packed) containing 2, 3 or 4 co‐axial nucleic acid chains per helical unit and having the phosphate groups near the outside.”
The notes from this lecture were used to inform James Watson and Francis Crick’s attempt to uncover the precise structure of DNA, and they finished building their model on 7th March 1953.
The paradigm shift
As John of Salisbury said: “We are like dwarfs sitting on the shoulders of giants. We see more, and things that are more distant, than they did, not because our sight is superior or because we are taller than they, but because they raise us up, and by their great stature add to ours.”. A huge amount of work preceded the work of James Watson and Francis Crick (this article has only scratched the surface).
But there is a reason that this particular discovery in the DNA timeline is seen through the lens of the Mandela Effect. Thomas Kuhn argued that science does not evolve gradually towards truth. Science has a paradigm which remains constant before going through a paradigm shift when current theories can’t explain some phenomenon, and someone proposes a new theory. The new paradigm better explains the observations and offers a model that is closer to the objective, external reality.
Knowing the exact structure of DNA has been such a tremendous paradigm shift, that the knowledge it has formed the basis of is almost inexhaustible. DNA replication, Transcription, Translation, DNA damage and mutation, DNA repair pathways, PCR, Sequencing, CRISPR, Epigenetics, Positive and negative supercoiling and much more.
When will the next major paradigm shift be? Unfortunately, I do not possess the wisdom to answer that but if I do have one nugget of parting wisdom before you go, it is this:
Make sure that when you draw DNA, you draw it as a right-handed helix, and not a left. Twitter will get very angry at you if you don’t.
Image Credit: Canva
