Meselson and Stahl studied DNA replication by culturing bacteria in a medium containing heavy nitrogen, $^{15}\text{N}$, until all the DNA had been labelled. These bacteria, called the parental generation, were then moved to a culture containing only light nitrogen, $^{14}\text{N}$, and allowed to replicate for two generations. DNA was removed from each bacterial generation and its relative mass was measured. The flow diagram shows the results. Which row accounts for the relative mass of the DNA in the second generation grown in $^{14}\text{N}$?
Biology 9700 · AS & A Level · Replication and division of nuclei and cells