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What is DNA?
Quick answer
DNA (deoxyribonucleic acid) is the molecule that carries the genetic instructions for building and running every living thing. It's a long, twisted ladder — a double helix — whose rungs spell out a code in four chemical letters. The four bases are adenine (A), thymine (T), guanine (G), and cytosine (C); A always pairs with T, and G with C.
Key things to understand
- The four bases are adenine (A), thymine (T), guanine (G), and cytosine (C); A always pairs with T, and G with C.
- The sequence of these letters is a code that tells cells how to build proteins.
- DNA is packaged into structures called chromosomes; humans have 23 pairs.
- A gene is a segment of DNA that codes for a specific trait or protein.
People also ask
Where is DNA found in the body?
In nearly every cell, mostly inside the nucleus. A tiny amount also lives in the mitochondria.
How much DNA do humans share?
About 99.9% of DNA is identical between any two people; the 0.1% difference accounts for our individual traits.
What's the difference between DNA and a gene?
DNA is the whole molecule; a gene is a specific stretch of it that carries instructions for one trait or protein.