If your hypothesis is that two proteins are working together in a complex for a particular cell function, would you expect to see them in the exact same places in a cell, when viewed by immunofluorescence microscopy?
a) Not necessarily, the proteins might only have partly overlapping localization patterns.
b) Yes, the proteins have to be in all the same places because otherwise they wouldn't stay folded in the proper conformations.
c) Yes, the proteins have to be in all the same places in a cell if they work together for a particular cell function.
d) Yes, because immunofluorescence microscopy only shows simple localization patterns, so the two proteins will either be completely the same places or completely different places.
Answer: A