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Speaker 1: This Day in History Class is a production of I

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Speaker 1: Heart Radio. Welcome to This Day in History Class, where

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Speaker 1: we bring you a new tidbit from history every day.

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Speaker 1: Today is April. The day was a nineteen fifty three,

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Speaker 1: scientists James Watson and Francis Crick announced their discovery of

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Speaker 1: the structure of DNA in an article in the journal Nature.

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Speaker 1: The article, titled Molecular Structure of Nucleic Acids, A structure

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Speaker 1: for deoxy ribos nucleic acid, began with the following statement,

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Speaker 1: we wish to suggest a structure for the salt of

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Speaker 1: deoxy ribos nucleic acid DNA. This structure has novel features

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Speaker 1: which are of considerable biological interests. Nature also published shorter

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Speaker 1: articles by scientists Maurice Wilkins and Rosalind Franklin, who had

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Speaker 1: contributed to the discovery, in that same issue after Watson

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Speaker 1: and Crick's article. In nineteen sixty two, Watson and Crick

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Speaker 1: and Wilkins received the Nobel Prize in Physiology or Medicine

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Speaker 1: for the discovery, but Franklin, who died in nineteen fifty eight,

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Speaker 1: did not receive widespread recognition for her contributions. The discovery

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Speaker 1: was a watership moment in the history of science, but

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Speaker 1: it was one that became mired in controversy. The nineteen

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Speaker 1: fifty three discovery of DNA structure came after decades of research.

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Speaker 1: A Swiss chemist named Friedrich Meischer identified DNA or what

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Speaker 1: he called nucleon as a distinct molecule in eighteen sixty nine.

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Speaker 1: In nineteen forty four, Oswald Avery and his colleagues published

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Speaker 1: a paper showing how jeans are composed of DNA, among

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Speaker 1: other observations about DNA structure. Austrian biochemists Irwin Chargaff found

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Speaker 1: out that at anine and thymine always appeared in equal amounts,

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Speaker 1: as did cytosine and guanine. By the early nineteen fifties,

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Speaker 1: thanks to the work of scientists like Phoebus Levine, researchers

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Speaker 1: knew that DNA was made of nucleotides, each of which

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Speaker 1: contains a base, a molecule of sugar, and a molecule

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Speaker 1: of phosphoric acid. The sugar was deoxy ribos in. The

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Speaker 1: four nitrogenous basis were at anine, guanine, cytosine, and thymine,

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Speaker 1: but researchers did not know exactly what DNA looked like

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Speaker 1: or how it was copied. In early nineteen fifty three,

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Speaker 1: chemist Linus Pauling proposed and an accurate model of DNA

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Speaker 1: that showed it as a three stranded helix. At the time,

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Speaker 1: Watson and Crick were working at the University of Cambridge.

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Speaker 1: Maurice Wilkins, Rosalind Franklin, and graduate student Raymond Gosling were

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Speaker 1: at King's College London using X ray diffraction to study DNA.

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Speaker 1: Franklin was experienced an X ray crystallography, a technique that

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Speaker 1: scientists used to determine the structure of crystals. When the

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Speaker 1: crystallized form of a molecule is exposed to X rays,

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Speaker 1: the X rays to fract inform a pattern that scientists

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Speaker 1: can use to understand the molecule structure. Franklin and Gosling

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Speaker 1: took an X ray diffraction photograph of a DNA molecule

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Speaker 1: known as Photo fifty one that looked like an X

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Speaker 1: and revealed the molecules helical structure. Wilkins, who spent time

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Speaker 1: at Cavendish Laboratory at Cambridge with Crick, ended up showing

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Speaker 1: Photo fifty one to Watson. Watson and Crick thrilled with

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Speaker 1: Photo fifty one and worried Pauling would beat them to

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Speaker 1: the punch, proposed a new model for DNA structure. Watson

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Speaker 1: and Crick did not do any of their own experiments. Instead,

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Speaker 1: they relied on drawing conclusions from existing data, including Photo

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Speaker 1: fifty one. The pair used data they got from an

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Speaker 1: informal report Franklin gave to scientists Max per Roots at Cambridge,

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Speaker 1: even though they didn't act Franklin for permission to interpret

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Speaker 1: the data. Ironically, Pauling had advanced the method of model

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Speaker 1: building that made Watson and Crick's discovery possible. Watson and

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Speaker 1: Crick shifted around cardboard cutouts of the molecules, and with

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Speaker 1: the help of chemist Jerry Donohue, eventually figured out the

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Speaker 1: structure of DNA. On February nine, fifty three, Watson and

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Speaker 1: Crick determined that DNA was a double stranded, anti parallel,

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Speaker 1: right handed helix. They found that the outside of the

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Speaker 1: helix is made up of sugar phosphate backbones, and the

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Speaker 1: inside is made up of hydrogen bonded pairs of the

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Speaker 1: nitrogenous basis. On April, the journal Nature published Watson and

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Speaker 1: Crick's findings, followed by articles from Franklin and Wilkins. In

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Speaker 1: the paper, Watson and Crick described the structure of DNA.

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Speaker 1: Krick's wife, O'Dell, created schematic drawing of the DNA double

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Speaker 1: helix that accompanied the text. The discovery fueled a ton

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Speaker 1: of scientific advancement, from DNA fingerprinting to genetic engineering. Franklin

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Speaker 1: died of cancer in nineteen fifty eight, four years before Watson, Crick,

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Speaker 1: and Wilkins were awarded the Nobel Prize. Nobel Prizes are

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Speaker 1: not awarded posthumously. Watson published a book on the discovery

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Speaker 1: of DNA structure in nineteen sixty eight. I'm Eves Jeff Coo,

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Speaker 1: and hopefully you know a little more about history today

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Speaker 1: than you did yesterday. If you like to learn more

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Speaker 1: about Rosalind Franklin, listen to the episode of Stuff you

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Speaker 1: Missed in History class called Rosalind Franklin DNA's Dark Lady.

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Speaker 1: Instagram or Facebook at t d I h C podcast,

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