This is a great activity for a substitute and I have used it with great success when the need arises, especially if students who finish it get a little extra credit. It is a simplified puzzle designed to help students understand a little more about how triplet (three-letter) codes can be used to code for meaningful things. In this case a triplet code using letters synonymous with those found in DNA is used to write a code for students to decipher and then follow the directions in the code to complete a simple drawing. Most high school students can finish in a single class period, but some may need to take it home. Students younger than high school age might take a few periods to complete it, or they can work in teams. The puzzle is a highly simplified, enjoyable way for student to gain familiarity with how codes like these work.