Final answer:
After the bleaching of fluorescently tagged cell surface molecules and incubation, the fluorescence will recover in the bleached area due to lateral diffusion of membrane molecules, illustrating membrane fluidity and dynamics.
Step-by-step explanation:
In the process described, cell surface molecules are labelled with a fluorescent tag, and then some of them are specifically bleached using a laser. This technique is known as fluorescence recovery after photobleaching (FRAP). After the bleaching event and subsequent incubation, one would observe that the fluorescence in the bleached area begins to recover as the bleached molecules move out and unbleached fluorescent molecules move back into the area. This movement is due to the lateral diffusion of the membrane molecules. Therefore, the initial observation is a dark spot where the laser has bleached the fluorescence, which gradually diminishes as the fluorescence returns.
The rate of recovery and extent of fluorescence intensity returning provide information on the mobility and dynamics of the membrane molecules. This technique is extremely useful in studying phenomena such as membrane fluidity, protein interactions, and the effects of various drugs on membrane components.