What colour hair have you got? Is it straight, wavy or curly? What colour are your eyes? Why are some people tall and slim while others are short and stocky? It's all in your genes. Each person on this planet is unique, because everyone has got a different combination of genes. These are contained in the DNA structure. Your genes determine your general shape and size, the colour of your skin, eyes and hair, the shape of your face, nose, ears, mouth and teeth.
For every part of your body you have got two genes. You inherit one from your mother and one from your father. One of the two genes is dominant, but you can pass either gene on to your children. Look at this couple, for example. The man and the woman both carry a gene for blue eyes and a gene for brown eyes, which they have inherited from their own parents, but they have both got brown eyes, because the brown gene is always dominant.
In this ideal example the couple have two sons and two daughters and each one has received one of the four possible combinations of the parents' genes. As we can see, one of them is blue-eyed and the other three have got brown eyes, but three of them carry a blue gene.
A gene can stay hidden in a family for generations. For example, the second daughter is married. Her husband's eyes are brown, but he also carries a blue gene. This couple has got four children and each child has got a different combination of the parents' genes. So one child has got blue eyes, although her parents and grandparents have all got brown eyes.
Knowledge about genes has been used since the eighteenth century to improve plants and animals. Scientists and farmers select the best possible specimens to breed from. In this way they have been able to produce bigger fruit and vegetables, animals that produce more meat, kinds of wheat or rice that are more resistant to disease, and so on. This is known as selective breeding.
Now scientists can actually identify the genes for particular characteristics. In the new science of genetic engineering, genes can be removed, added or replaced to produce the characteristics that --we want. New and better plants and animals will be produced by genetic engineering. Will we be able to design the perfect human being, too? 'Nobody's perfect', we say. Perhaps one day everyone will be.