Everything comes from your genes - and they come from your mum and dad. A gene is the basic unit of inheritance which you can find in all living things. It is a set of coded instructions, built up from DNA molecules. It's these instructions that make you you and me me. Each gene is connected to a whole lot of others to form chromosomes. Genes control your inherited characteristics like your eye or skin colour, whether you grow feathers or fur.

Every time a cell divides (as you grow, for example), a perfect copy of its genes is made. Just occasionally, this copying goes slightly wrong in which mutations or gene shuffling, called recombination, happens. It is these 'mistakes' which allow evolution to happen by trial and error. But genetic engineers deliberately insert new genes by recombination although they cannot tell where the genes they add will end up. So the process is random and may alter the way the new organism's genes behave in a way no-one can predict. [1] This is one of the main reasons people are so worried about GE. These transgenic organisms are, like Dr Frankenstein's monster, 'bolted together' out of bits of others. This is why GE foods are called 'Frankenfoods' by protest groups. The monster in the Frankenstein story ends up killing his creator's loved ones... which I hope will not happen with GE creations. And did you know that the original Frankenstein appears in a classic horror story published in England by the rather visionary Mary Shelley way back in 1818?
[1] New Scientist, 17/4/99, 19