How you look, how tall you are, whether your hair is straight or curly—all these and more are decided by your genes. Genes are the set of coded instructions found in every cell in your body. Your genes are unique to you (unless you are an identical twin, in which case you share this code with your twin). They contain all the information your body needs to develop, grow and maintain itself through life.

DNA

Coiled up inside the nucleus of each of your body’s cells are long strands of a substance called DNA. Seen under a powerful microscope, DNA looks like a twisted ladder. The “rungs” of the ladder are made of four different chemical units, linked in pairs. There are millions of rungs. The order of the units down each ladder forms an extremely long and detailed code. This contains the instructions your body needs to grow, develop and work properly.

Inheritance

Your genes come from your parents. You inherit (get) half from your mother and half from your father. This is why you look a little like both of them. Genes are also responsible for the tendency to develop certain diseases that run in some families. These are called genetic disorders. Luckily, they are quite rare. Scientists can now identify some of those disease-causing genes and find ways to correct them.

Identical twins

When an egg cell splits in two soon after it is fertilized, identical twins develop. They are always the same sex and share identical features, such as eye and hair colour. They look the same because they have exactly the same genes.