"The way DNA encodes information is analogous to how we arrange the letters of the alphabet into words and phrases with specific meanings. The word rat, for example, evokes a rodent; the words tarand art, which contain the same letters, mean very different things. We can think of nucleotides as a four-letter alphabet. Specific sequences of these four nucleotides encode the information in genes. Many genes provide the blueprints for making proteins, which are the major players in building and maintaining the cell and carrying out its activities."