9700/13 Biology Oct Nov 2010 Online Test | Cambridge AS and A Level MCQ
Scientists grew bacteria in a medium containing heavy nitrogen, 15N, as the only source of nitrogen. After many generations, both strands of all of the bacterial DNA molecules contained heavy nitrogen.
These bacteria were then moved from the heavy nitrogen medium into a medium with only light nitrogen, 14N. The bacteria divided once to form the first generation and once more to form the second generation.
A sample…