DNA is shaped like a long twisted ladder, and pairs of bases form the ladder's steps. Bases are known by the letters A, T, C, and G. It's the DNA alphabet soup! In DNA, bases only pair in two ways: T only pairs with A, and G only pairs with C. When a cell "reads" a long string of these letters (genes), it gets information on how to grow and develop.

Image credits: main image, Kelvin Chan.