KVPY SX SB Exam 19-Nov-2017 Question Paper

Matthew Meselson and Franklin Stahl grew E.coli (doubling time is 20 min) in medium containing ${}_{}^{15}\mathit{N}{\mathit{H}}_4\mathit{C}\mathit{l}$ for many generations.
Then the E.coli was transferred to medium containing ${}_{}^{14}\mathit{N}{\mathit{H}}_4\mathit{C}\mathit{l}$. After 40 minutes, the cells were harvested and DNA was extracted and subjected to cesium chloride density gradient centrifugation. The proportion of light and hybrid DNA densities will be