Have you ever looked in a mirror and noticed that if you lift your left hand, your mirror-image raises their right hand? Like your hands, a molecule and its reflection can be different, a property called “chirality” (from the Greek word for hands), and most of the molecules that make up our bodies are chiral. This lesson looks at the chirality of DNA, the molecule that makes our genes, and how the “handedness” of DNA determines its structure and behavior. This module is best presented after students have learned about the chemical structure of DNA, base-pairing, and the double-helix. Students can further expand their understanding of DNA's structure and function by learning learn how natural, “right-handed” DNA and its unnatural mirror image, “left-handed” DNA, look different at a chemical level, and then use a simple origami method to build three-dimensional models of “right-handed” and “left-handed” DNA. By studying these models, they will learn how molecular chirality determines the higher-order structure of DNA (the “double-helix”), and how these differences determine how DNA interacts with itself by base-pairing, and how it interacts with the enzymes which read DNA. By the end of the lesson, students should understand how the fundamental chemical concept of chirality relates to biology, why “homochirality” is a defining feature of life, and have the opportunity to discuss how this relates to the origin of life on Earth and what “alien” life might look like if we found it on other planets.