In Figure 8.3, there are black squiggles in the RER compartment. Chemically, what specifically is the blackness in this picture? (see the figure to right) What is the blackness an indicator of (as explained in the pulse-chase video)? Autoradiography Sample Radioactive part of sample AgCl crystal Agmetal Cover with photographic emulsion Radiation activates the closest Ag+ ions Reduce the activated Ag+ to Ag metal | Wash away soluble Ag+ leaving insoluble Agmetal.