Bacteria were grown in a medium containing heavy isotope of nitrogen (N15) for many generations and all their DNA contained heavy nitrogen only. A bacterium of this type was transferred to normal medium and allowed to duplicate. After two divisions of heavy DNA,
Correct answer: B. Two daughter cells have normal DNA and other two have heavy DNA
- A. Only one daughter cell will have heavy DNA
- B. Two daughter cells have normal DNA and other two have heavy DNA
- C. All daughter cells have heavy DNA
- D. Half daughter cells have heavy DNA and other half have normal DNA
Explanation
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.
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About Chromosomes
Chromosomes are DNA-protein structures that carry genes and become visible during cell division. Coverage includes chromatin, centromeres, sister chromatids, homologous chromosomes, chromosome number, and the distinction between diploid and haploid cells, with links to DNA replication, mitosis and meiosis.
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