““Parts of it are surprisingly beautiful. On a vast stretch on chromosome eleven, for instance, there is a causeway dedicated entirely to the sensation of smell. Here, a cluster of 155 closely related genes encodes a series of protein receptors that are professional smell sensors. Each receptor binds to a unique chemical structure, like a key to a lock, and generates a distinctive sensation of smell in the brain—spearmint, lemon, caraway, jasmine, vanilla, ginger, pepper. An elaborate form of gene regulation ensures that only one odor-receptor gene is chosen from this cluster and expressed in a single smell-sensing neuron in the nose, thereby enabling us to discriminate thousands of smells.””
