From the moment of conception, the DNA strands contained in the chromosomes of our cells are hard at work duplicating themselves, so that the body can make and maintain all the different parts it needs to function efficiently. What DNA does and how it does it is explained by Dr Balkwill's straightforward text and Mic Rolph's illustrations. This is the third book in a series which introduces microbiology to young readers. The first two titles, Cells Are Us and Cell Wars, won the 1991 Copus Science Book Prize.