DNA: The Molecule That Encodes You

Deoxyribonucleic acid—DNA—is the molecule that carries the genetic instructions used to build and run almost every living thing. Its structure, discovered by Watson, Crick, Franklin, and others, is the famous double helix: two strands wound around each other, held together by hydrogen bonds between paired bases.

There are only four bases: adenine (A), thymine (T), guanine (G), and cytosine (C). A always pairs with T, and G with C. The order of these letters along the strand is the "code." Long stretches of DNA—genes—are read by the cell and used to build proteins. Proteins then do most of the work in the cell: structure, enzymes, signalling, and more.

When a cell divides, the two strands of DNA separate and each acts as a template for a new partner strand. That way, each new cell gets a full copy of the genome. Mistakes in copying (mutations) can cause disease, but they also provide the variation that drives evolution.

Learning how DNA works is the foundation of genetics, medicine, and biotechnology.