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Bacteria were grown in a medium containing heavy isotope of nitrogen ($N^{15}$) for many generations and all their $DNA$ contained many heavy nitrogen only. A bacterium of this type was transferred to normal medium and allowed to duplicate. After two divisions of heavy $DNA$ is likely to be that
Only one daughter cell will have heavy $DNA$
Two daughter cells have normal $DNA$ and other two have both normal and heavy $DNA$
All daughter cells have heavy $DNA$
Half daughter cells have heavy $DNA$ and other half have normal $DNA$
Solution
(b) After two divisions, four bacterial cells are formed in which two daughter bacterial cells have normal $DNA$ and other two have both normal and
heavy $DNA$ because $DNA$ replicates by semiconservative method in bacteria.
