The answer is: There will be more mold on the moist slice and still none of the dry slice.
Molds belong to the kingdom Fungi. They are multicellular fungi consisting of multicellular filaments (hyphae). For growth, all molds need moist surface. This is the reason why in Gene's experiment, the only moist slice of bread was moldy. They have short life cycle, so 5 days were enough for molds to cover 50% of moist slice. Extended period of time will allow molds to spread more through moist surface if the surface remain moist.
The answer is electrophoresis. The electrophoresis can separate different length of DNA fragments using the agarose gel. The principle is that the DNA has negative charge and under constant volt it will move from negative to positive. And the longer the DNA is, the slower the DNA runs.