The object of the present invention is to utilize a reinforcing plate formed out of a metal or a hard resin introduced into a key unit in order to overcome the weak point that conventional rubber keypads are too soft and lack shape stability, as a design element of equipment including a key unit into which the plate is incorporated. The handle member may be configured to be capable of closing a receptacle in a leaktight manner. Axial space is economized by eliminating traditional spider retaining rings. The marker gene product can be an antibiotic resistance gene that confers antibiotic resistance by stoichiometrically binding to the antibiotic or it can be a fluorescent protein region.