To stay healthy, your cells must continuously perform a wide variety of chemical tasks. Your DNA genes, in the nucleus of every cell, help orchestrate this activity. A cell uses its genes as a kind of biochemical cookbook: whenever it has to do anything, a cell looks up the recipe in its DNA. It then uses this recipe to cook up whatever proteins it needs to get the job done. Your cells are hard at work right now, creating thousands of tailor made proteins for thousands of different biochemical jobs. Sometimes, however, things can go wrong. When a virus attacks, it injects its own DNA into one of your cells. Like your own genes, the viral DNA contains recipes. Unfortunately, these recipes are only good for making new viruses.

为了保持健康，你的细胞必须不断地进行各种各样的化学反应。你的DNA基因，存在于每一个细胞的细胞核，会帮助协调这项活动。细胞用它的基因作为一种生化食谱：无论何时细胞在工作的时候，它都要在DNA查询配方。然后，它使用这个配方来烹煮蛋白质所需的物质，从而完成化学反应。此刻你的细胞都在努力工作，创造数以千计由蛋白质形成的裁缝来完成数千项不同的生化反应。然而，有时候，事情会出差错。当病毒攻击时，它将自身的DNA注入到你的细胞中。像你自己的基因一样，病毒的DNA也包含有食谱。不幸的是，这些食谱只对产生新的病毒有利。