Bacteria were grown in a medium containing heavy isotope of nitrogen $\left(N^{15}\right)$ for many generations and all their DNA contained many heavy nitrogen only. A bacterium of this type was transferred to nomal medium and allowed to duplicate . After two divisions of heavy DNA is likely to be that a. Only one daughter cell will have heavy DNA b. Two daughter cells have normal DNA and other two have both normal and heavy DNA c. All daughter cells have heavy DNA d. Half daughter cells have DNA and other hald have normal DNA

Sure, here are the step by step solutions: 1. The parent bacterial cell has one copy of DNA that is initially normal (N). 2. The cell undergoes DNA replication, resulting in two copies of DNA that are each half normal (N) and half heavy (H). 3. The bacterial cell begins to divide, with each daughter cell receiving one copy of DNA. 4. The first division results in two daughter cells, each with one copy of DNA that is half normal (N) and half heavy (H). 5. The second division results in four daughter cells, each with one copy of DNA. 6. Two of the daughter cells have normal (N) DNA, which came from the original parent cell. 7. The other two daughter cells have both normal (N) and heavy (H) DNA, which came from the replicated DNA in the parent cell. 8. This is because DNA replication in bacteria follows the semiconservative method, where each new DNA molecule contains one strand from the original molecule and one newly synthesized strand.