How exactly do all those letters in DNA code for making a living thing? The short answer is that the code of letters in DNA is a recipe to make proteins. Proteins form structures, enzymes or other chemicals to create the building blocks of organisms and maintain homeostasis. When a cell needs to make a protein, say the enzyme to digest lactose (the sugar in milk), it needs to use/read the DNA code to make proteins. We call this process protein synthesis. Protein synthesis requires the use of DNA and all three forms of RNA to read the code and make the desired protein. This occurs in two steps: