How many protein-coding genes are in the human genome?
Before the Human Genome Project finished, many biologists expected a creature as complex as a person would need well over 100,000 genes. The final tally came in far lower than almost anyone had guessed.
Reveal the answer
About 20,000 protein-coding genes — roughly the same number as a mouse, and only a third more than a tiny roundworm. Human complexity turns out to come more from how genes are combined and switched on than from how many of them there are.