Find out the number of base pairs in E.coli DNA if its DNA is 1.36 mm long.

In the given case, the number of base pairs for E. coli would be 4 x 10⁶ bp. It can be calculated as Average distance between two base pairs of DNA is 3.4$\stackrel{\mathrm{o}}{\mathrm{A}}$. Length of E. coli DNA is: 1.36x 107$\stackrel{\mathrm{o}}{\mathrm{A}}$
So, number of nucleotides = $\frac{1.36 \mathrm{x} {10}^7 {\displaystyle \stackrel{\mathrm{o}}{\mathrm{A}}}}{3.4 {\displaystyle \stackrel{\mathrm{o}}{\mathrm{A}}}}=0.39 \mathrm{x} {10}^7=3.9 \mathrm{x} {10}^6\cong 4 \mathrm{x} {10}^6 \mathrm{bp}$