What makes you human or me a penguin? Genes. These are the instructions for how to build a body which all living things have.




Tiny creatures like snails have them just as big animals like whales do. So do all plants and other living things. Genes are very tiny clumps of information about how to make parts of living bodies … a little like a recipe for a cake or a music track on an old-fashioned cassette tape or CD. But they don't just exist on their own. They are packaged up in long strings called chromosomes like a whole music album on tape.

All these genes - that's all the instructions needed to make you or me - are stuffed in the middle of tiny blobby packets called cells. Cells themselves are very tiny but as millions and millions of them stick together, what we call a bodyScientists call this the phenotype begins to form. That could be a snail, a whale; you or me. (How this 'sticking together' happens is very complicated and no-one yet understands it fully.)

When you grow, some of your millions of cells split into pairs of identical new ones. Start with one million and, whooo! - you've got two million - twice as big! Now this is the clever bit: all the gene instructions get copied exactly just before the cells split. This is like copying your music album onto another blank CD to give to your friend. So every cell of every body of every living thing on the planet always has this gene body-building information - the genetic code - inside it.

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