Mammalian cells were grown in a cell culture medium that contains large amounts of uracil labeled with radioactivity on the two nitrogens in the uracil ring.  Assume that this radioactivity nitrogen remains in uracil and cannot be transferred to any other molecule.  Which of the following molecules would probably contain radioactivity? 

1. DNA
2. RNA
3. Protein
4. Glycogen
5. Fatty Acids