How DNA works
DNA runs cells by remote control. instead of organizing a cell directly, it instructs the cell to make proteins. These complex and varied chemicals have many different roles. A molecule of DNA can hold the coded plans for thousands of different proteins, the length of DNA that codes for each of them is known as a gene. Proteins are assembled by linking together chemical units, called amino acids, in an exact order. There are 20 different amino acids, but DNA has to specify them using just four different chemical "letters" , or bases (p.34). So how does it do this? The answer was suggested not by a biologist, but by the astronomer George Gamow, in 1954. He thought DNA might use "words" made up of three letters and, as events proved, his guess was right.