CBSE 2024 · Region 3 · Set 1 · Q8 · 1 mark

In an experiment, E. coli is grown in a medium containing $\displaystyle { }^{14} \mathrm{NH}_{4} \mathrm{Cl}$. ( $\displaystyle { }^{14} \mathrm{~N}$ is the light isotope of Nitrogen) followed by growing it for six generations in a medium having heavy isotope of nitrogen $\displaystyle \left({ }^{15} \mathrm{~N}\right)$. After six generations, their DNA was extracted and subjected to CsCl density gradient centrifugation. Identify the correct density (Light/Hybrid/Heavy) and ratio of the bands of DNA in CsCl density gradient centrifugation.

CBSE Class 12 Biology past-paper question from the 2024board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.