Code is a system of words, letters, or signs used to represent a message in a secret, shorter or in a convenient form. DNA (deoxyribonucleic acid) is such a code to all living cells in the universe. DNA holds the instruction manual for each living thing for anything from a blade of grass to bacteria, animals, and humans. But what exactly is DNA, and how did we discover it? Even centuries ago, scientists knew that there was some microscopic molecule inside organisms that encoded its characteristics - causing similar traits to be passed down to offspring. However, scientists were unsure about what this molecule could be. In the 1950s, scientists named the "gene" to be this very microscopic molecule. This elusive "gene" was capable of replicating with little to no error, a biological machine that is key to all life as we know it. The chemistry, structure, and replication of genes were unknown to scientists. Only after all the main groups of macromolecules—proteins, sugars, and lipids—were ruled out, was an amazing discovery about to occur. Watson & Crick are credited to have discovered the double helix structure of DNA (Figure 1).
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