What is DNA?

What does DNA do in our cells, and what does a 'DNA sequence' look like?
20 July 2020

Interview with 

Eva Higginbotham


Coming up, we’ll hear about Rosalind’s life and work, including hearing from her younger sister, Jenifer, and where the DNA revolution she helped to kick start is taking us today. But first, what actually is DNA? Recently, Eva Higginbotham took a windy bike ride in the July sun down to the south of Cambridge, along a cycle path painted like coloured piano keys stretching into the distance as far as she could see...

Eva -Although the path was created in 2007, the metaphorical foundations for this path were laid back in 1953 through the work of somebody whose birthday it is on the 25th of July, who would have been 100 years old - Rosalind Franklin. You see, this is the DNA cycle way, and Rosalind Franklin’s research was part of what set us on the path to really understanding DNA. DNA is the material unique to each of us that lives in our cells and contains all the instructions for not just what that cell has to do, but for how to build your entire body. Now DNA stores this incredible amount of information very elegantly in the form of a long sequence of different molecules called nucleotide bases and there are 4 types: adenosine, thymine, guanine, and cytosine, A T G and C, and just like the path, where the bases are represented by the different colours, they are in a long sequence one after the other, in what appears at first glance to be random order, but is actually not random at all, because it’s the order of these As, Ts, G, and Cs that makes up specific genes, which in turn codes for the specific proteins and other products which make up our cells. In fact, if I kept going south, I would come to the Sanger Institute, a research institute named after Fred Sanger who invented the first method to figure out the order of bases in a piece of DNA in a process called sequencing. The path I walked on goes on for over 10,000 yellow, green, red, and blue ‘bases’, and represents the genetic sequence of the BRCA2 gene, mutations in which can cause breast cancer. It’s also rather busy, and next to the railway tracks. Rosalind Franklin sadly died at only 37 of ovarian cancer, but it’s partly down to her research into the structure of DNA that we know that not only does DNA have bases, but is actually made of two long strands of molecules called phosphates with the bases stuck in between, and those two strands stick together because the bases like to pair up with each other. A’s bind with Ts, and Gs bind with Cs. You can think of it like a ladder, where the horizontal rungs are the bases and the vertical bits are the phosphate backbone. Apart from DNA is more like if you twisted the ladder to form a sort of corkscrew, in other words, a helix. The reason we know DNA is a helix is thanks to Rosalind Franklin’s experiments using a technique called X-Ray crystallography, but the story of that discovery isn’t exactly straightforward. So as my walk down the DNA cycleway came to a close, let’s walk back in time to find out more about Rosalind’s life and work. And what better place to start than in Cambridge, where Rosalind got her start as a scientist.


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