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 of bacteria was collected from the second generation and the DNA was analysed to find:
● the percentage of DNA strands that contained only light nitrogen
● the percentage of DNA molecules that contained light nitrogen and heavy nitrogen.
Which row shows the results of this analysis?
1 )
A
2 )
B
3 )
C
D
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