DNA Structure
Free printable DNA structure diagram — the double helix, sugar-phosphate backbone and base pairs (A-T and G-C), all labeled. Download a high-resolution PDF or PNG for Letter paper.
The parts of a DNA molecule
DNA is the molecule that carries the instructions for building and running a living thing. It is shaped like a twisted ladder called a double helix. Here is what happens at each labeled part of the diagram:
| Part | What it does |
|---|---|
| Double helix | The twisted-ladder shape of a DNA molecule. |
| Sugar-phosphate backbone | The two long strands that form the sides of the ladder. |
| Base pairs | The rungs of the ladder, each made of two bases joined in the middle. |
| A pairs with T | Adenine always pairs with Thymine. |
| G pairs with C | Guanine always pairs with Cytosine. |
Companion worksheet
A free fill-in worksheet with an answer key, built from the labels above — students match each part to its description, then answer a couple of short questions. Great for a quick check after using the diagram.
How to print
Choose Download PDF for a ready-to-print file that fits US Letter paper (8.5 × 11") in landscape, or Download PNG for the high-resolution image.
Frequently asked questions
What are the base pairs in DNA?
Adenine (A) always pairs with Thymine (T), and Guanine (G) always pairs with Cytosine (C). These pairs form the rungs of the DNA ladder.
What is the shape of DNA?
DNA is shaped like a twisted ladder called a double helix.
What paper size should I print this on?
The diagram is sized for standard US Letter paper (8.5 × 11") in landscape orientation. Use "Download PDF" for a print-ready file that fits the page automatically.