Why won't this experiment work?

It should be noted that amino acids are also equipped with nitrogen atoms which means that it also contains proteins. The main goal of the experiment is to distinguish between the DNA and proteins but this is not possible if both of them have it.

The radioactivity will not be useful in checking what’s wrong. It is best if the two students would think of another project that may produce more productive results. It will also be advisable if they would also think of making other changes or modifications to the experiment that they want to re-do.