Image from x-ray crystallography contributes to the discovery of the double helix structure of DNA

contributed by Dan Turner @danbtweeter, turne400 [at] msu [dot] edu

Keywords: 

DNA, Europe, Fundamental research, Historical figure, Lab, Molecular biology, Observational, Woman

Slides

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Other Resources

Franklin, R.E. and Gosling, R. G. Nature. Molecular Configuration of Sodium Thymonucleate. (1953).

Presentation Notes

Researcher’s Background

Franklin was a chemist/molecular biologist who was instrumental in discovering the double helical structure of DNA and virus structure.

Biography in brief

Rosalind Franklin was a chemist/molecular biologist known for using science as a tool to explain how the world works. Her bold work ethic and honest personality led to her position working on the structure of DNA with her PhD student Raymond Gosling. Franklin published her x-ray crystallography images of DNA in Nature in 1953, detailing the double helix structure DNA and phosphate-sugar backbone of DNA. After working with DNA, she moved onto influential work with the physical structure of virus. She died at the age of 37 from ovarian cancer.

Axes of identity & underrepresentation

Rosalind Franklin helped discover the structure of nucleic acids through her work with x-ray crystallography. Her images of DNA, demonstrating the specifications and helix structure of DNA, from the 1950s were shared by Maurice Wilkins with James Watson and Francis Crick before they finished their physical model of DNA, without her knowledge.

Research Overview

Take home message of study

X-ray crystallography, a technique to determine the structure of molecules and crystals, was used in the 1950s at a very high resolution to help determine DNA’s double-helix. Here, Rosalind Franklin and her PhD student Raymond Gosling support the early idea, at the time, that phosphate is vital to the backbone of DNA while nucleotide bases are turned toward the middle of the helix. The image featured in the paper is widely known as “Photo 51.”

Study system

DNA’s double helix structure, comprised of a sugar-phosphate backbone and nucleotide core, was debated for many years before more evidence supported the idea. With the contribution of Rosalind Franklin’s x-ray crystallography image to James Watson and Francis Crick’s physical DNA model, we now understand how these nucleotide, phosphate, and sugar groups form to make DNA.

Key Research Points

Main contributions/Key Figure

After measuring the distances between the dark spots at the top and bottom of the photo, Franklin and Gosling then ran a series of calculations to find the distance between nucleotide bases in the helix. They also found that the vertical distance between the dark spots in the center of the photo were related to the distance between phosphate molecules. Finally, the “X-shaped” cross in the middle of photo contains ten “layers” of black spots, indicating a series of 10 base pairs per “turn” of the DNA helix.

Societal Relevance

Specimens, particularly of extinct species, allow us to learn more about that species. Once we know more about them, we can understand their role in an ecosystem (e.g., food for other animals), how we might be able to stop them from going extinct, how the species that are present today evolved from species in the past that are now extinct, and a lot of other information. Data that these two individuals collected nearly 100 years ago also helps us today! They collected data on the location of pika – a small mammal which is an ‘indicator species’. Data on how location of pikas changes over time can help us to understand climate change.