In this lesson you learn what DNA is, what it does in your body and how it works, starting from zero. DNA is the instruction book inside your cells: a very long molecule that carries the instructions for building and running a living thing.

Every plant, animal, mushroom and bacterium has DNA. Yours came from your parents, and it is part of the reason you have your eye colour, your blood type and much more.

Below is a small piece of DNA. It looks like a twisted ladder. Spin it, unzip it and look at the letters on the rungs.

In this lesson you'll:

• find where DNA lives in your body, and how 2 metres of it fits inside a single cell
• read DNA's four-letter code and the one rule that pairs its letters
• follow a gene as it becomes a protein, the molecules that do the work in your body
• see how DNA copies itself, what happens when a letter changes, and why you are a mix of your parents

It takes about 60 minutes. Each step has an animation to play with, and each one uses what you learned in the step before.

Takeaway: DNA is a long, twisted ladder of letter pairs that holds the instructions for building you.