The Double Helix
Context:
The discovery of the double helical structure of the DNA molecule in 1953 by James Watson and Francis Crick is considered one of the biggest breakthroughs in Science.
This twisted ladder structure has become so iconic that it serves as a shorthand to represent Science itself.
About the Structure
The double helix is the three-dimensional structure of DNA (deoxyribonucleic acid) containing the genetic information of an individual
The final Watson-Crick model consists of two long, parallel strands held in a chain by sugar and phosphate compounds
These strands are connected by pairs of four nitrogen-containing compounds (bases):
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
A key feature is the complementarity of the base sequences.
The Adenine on one strand always pairs opposite the Thymine on the other, while Cytosine is always paired opposite Guanine
The Discovery
Watson and Crick used three-dimensional wooden models to build a structure that matched information provided by other scientists
Critical clues came from X-ray crystallography.
A historic X-ray photograph called Photo 51 taken by Raymond Gosling under the supervision of British chemist Rosalind Franklin showed the double-helix structure
Watson and Crick saw this photo and Franklin's unpublished data, which served as the basis of their DNA model.
Franklin's contribution was critical to the discovery
Scientific Impact
The discovery revealed how individual traits are passed on from one generation to another
The structure's most important feature was that it clearly showed how genetic information could be replicated.
The two strands can separate, and the information on each one is enough to build a new, separate second strand
This sparked new fields like molecular biology, biotechnology, gene modification, and gene editing.