What is a gene?
A gene is a short stretch of DNA that carries the instructions for one specific job in your body — usually, building a particular protein.
Think of your DNA as a very long recipe book. A gene is a single recipe in it. Each recipe tells your cells how to make one thing — an enzyme that digests milk, a protein that builds muscle, a pigment that colours your eyes.
Humans have around 20,000 of these protein-coding recipes. Most of your DNA, interestingly, is not recipes at all; it does other regulatory work or has jobs we are still figuring out.
Last reviewed 29 May 2026 · reviewed by someone with genetics training