Soon after the Earth's creation, living cells began growing in deep-sea volcanic vents, sucking energy from the chemical brew that erupted from the ocean floor.
The most successful cells used string-like DNA molecules to store their precious genetic information. Working like tiny computer programs, the DNA sequences contained instructions for assembling the proteins that powered and maintained cell activity. Each set of instructions is called a "gene."
The ladder-like molecules could also split apart and duplicate themselves, passing the information to new generations, and creating a complex toolkit of genes.
