The blue arrows represent the obvious route to RNA, going from prebiotic compounds (marked here by 7,8, and 10) to nucleobases (3) and ribose (4). And the big red X shows the point at which this route fails.
Sutherland and his colleagues started with the same ingredients, but cooked them in a different recipe, marked in green. Instead of trying to build the two parts independently, the scientists instead built a single molecule that had more and more components of the two parts already in place. They used just four reactions, all of which worked efficiently, to get one of the four ribonucleotides, known as cytidine. At the end of the process, the scientists zapped the mix with ultraviolet light (something that would be easy to come by on the early Earth, unprotected by an ozone layer). They eliminated some of the unwanted side products and turned some of the cytidine into another unit of RNA, known as uracil.
The Recipe of Life. You think the food network would be interested in a show?