Zoology - Molecular Basis of Inheritance Question with Solution | TestHub

E. coli divides in 20 minutes. In three hours it will divide$\frac{180}{20}=9\mathrm{ }$times. After 9 divisions, the number of cells will be$2^9$. E.coli which will neither float nor sink in the test tube on ultracentrifugation with CsCl will have one heavy${\mathrm{N}}^{15}$strand and one light${\mathrm{N}}^{14}$strand. One E.coli with hybrid DNA will divide to form one E.coli with hybrid DNA and one E.coli with DNA with both N15 strands. Thus, the proportion of E.coli with hybrid DNA is$\frac{1}{2}$. When it divides for the second time, the proportion of E.coli with hybrid DNA is$\frac{1}{4}.$Thus, it can be noted that in this example, the proportion of E.coli with hybrid DNA can be represented as$\frac{1}{2^n}$where n is the number of divisions