An image forming apparatus includes an image reading section that reads an image on paper to generate image data, and an image forming section that forms on paper an image based on image data. The container system features a first container having a first container body. The pinion shaft support structure includes stepped portions formed on end surfaces of the pinion shafts and a fall-out prevention washer which is mounted on the carrier to be capable of locking the stepped portions. In a preferred embodiment, the reaction chamber is an amplification chamber for amplifying nucleic acid in the sample, and the separation region comprises an electrophoresis channel containing a suitable matrix material, such as electrophoresis gel or buffer, for separating nucleic acid fragments.