To solve this problem, we need to understand why a mutated gene does not appear on a photographic film when using a radioactive probe. Let's analyze the options:$\newline \bullet$Option 1: Mutated gene partially appears on a photographic film.$\newline$ - This option suggests partial appearance, which is not accurate for a probe with no complementarity.$\newline \bullet$Option 2: Mutated gene completely and clearly appears on a photographic film.$\newline$ - This option suggests complete appearance, which would only occur if the probe had complementarity.$\newline \bullet$Option 3: Mutated gene does not appear on a photographic film as the probe has no complementarity with it.$\newline$ - This option correctly states that without complementarity, the probe cannot hybridize, and thus the gene does not appear.$\newline \bullet$Option 4: Mutated gene does not appear on photographic film as the probe has complementarity with it.$\newline$ - This option is incorrect because complementarity would result in hybridization and appearance on the film.$\newline$Therefore, the correct explanation is that the mutated gene does not appear on a photographic film because the probe has no complementarity with it.$\newline$This corresponds to Option 3.