Bacterial cells have only one DNA molecule, which is double stranded and is replicated in essentially the same fashion as in eukaryotes. Imagine that, following the techniques of other scientists studying DNA, you created a bacterial cell that contains only radioactive nitrogen in its DNA. You then place the cell in a growth medium containing only "regular" (nonradioactive) nitrogen. Based on this scenario and your knowledge of DNA structure and replication, how many cells will contain some DNA with radioactive nitrogen after four rounds of cell replication?