And these two DNA molecules are essentially identical, assuming that process was mitosis. Now, let's actually discuss what this experiment consisted and how it showed that the semiconservative replication process was correct. So what they did initially was they wanted to grow these special bacterial E. Coli cells that contain labeled DNA molecules. So radioactively labeled DNA molecules. And the way that they did that is they took a medium that was very high, very rich in isotopic nitrogen atoms. So m 15.