And notice we also had a single band just like in this case. But this band was shifted to the left along this diagram, along the photograph. And what this basically means is we have a single type of DNA molecule because we have that single band but it is lighter, less dense than in this particular case because it is found farther to the left along the x axis. And that essentially confirmed the fact that after one generation, after one cycle we form one type of DNA molecule that consists of one radioactively labeled strand and one newly synthesized strand that contains the lighter N 14 isotopes. And so this is what we saw. So one of these was N 15 and the other one was N 14 because it was synthesized using the nitrogen atoms that had an atomic mass of 14 and not 15.