The Genetic Revolution

From the discovery of DNA to the dawn of gene editing in less than 200 years.

- Laura Mears

In the 1800s, Swiss biologist Friedrich Miescher discovered something strange. When he broke open the nuclei of white blood cells he found a substance rich in phosphorous unlike anything he’d seen before. He named it nuclein. We now know it as DNA.

DNA stands for deoxyribonucleic acid. Thanks to the work of Russian-born American scientist Phoebus Levene we know that it has three parts. The phosphorous that Miescher noticed connects to a pentagon-shaped sugar called deoxyribose. This, in turn, links to a nitrogen-containing structure known as a ‘base’. Four different bases make up the chemical letters of the genetic code, and the sugars and phosphates join them together into long strings.

The four DNA letters are adenine, cytosine, guanine and thymine. We know them most commonly by their first letter abbreviations: A, C, G and T. In a piece of DNA, the amount of A matches T and the amount of C matches G, but it wasn’t until James Watson and Francis Crick that we found out why. This Nobel Prize-winning pair revealed the structure of the molecule.

Rosalind Franklin and Maurice Wilkins had taken a picture of DNA using X-rays. Using their images, along with cardboard cutouts of each of the DNA bases, Watson and Crick played with possible configurations. In 1953, they finally revealed that DNA is a double helix.

Two strands of code form a pair that wind around like a twisted ladder. The bases on one strand cling to the bases on another via interactions called hydrogen bonds, forming the ladder’s rungs. The sugars and phosphates form the sides of the ladder, or the ‘backbone’. Space between the rungs allows other molecules to read or copy the code.