DNA Explained: Structure, Bases and What It Does
DNA (deoxyribonucleic acid) is the molecule that stores the instructions for building and running a living thing. Every cell in your body carries a complete copy.
The structure is elegant once you see it, and it explains how traits pass from parents to children.
The double helix
DNA looks like a twisted ladder — the famous double helix. The two long sides are made of sugar and phosphate. The rungs are made of pairs of chemicals called bases.
The four bases and base pairing
There are only four bases: adenine (A), thymine (T), cytosine (C) and guanine (G). They always pair the same way — a key idea called complementary base pairing.
- •A always pairs with T.
- •C always pairs with G.
- •This rule lets DNA copy itself accurately before a cell divides.
How DNA carries information
The order of the bases along the ladder is a code. Short sections called genes spell out instructions for making proteins, and proteins do most of the work in your body. Change the order of the letters and you can change the instruction — that is the basis of genetic variation.
Frequently asked questions
What are the four bases of DNA?
Adenine (A), thymine (T), cytosine (C) and guanine (G).
What pairs with what?
A pairs with T, and C pairs with G. This is called complementary base pairing.
What is a gene?
A section of DNA that contains the instructions to make a particular protein or carry out a function.