A researcher transforms 0.8 µg of a 4,500 bp plasmid DNA into competent *E. coli* cells and obtains $9.6\times 10^6$ colonies on selective plates. Calculate the transformation efficiency expressed as the number of transformants per microgram of DNA.

Step-by-step solution

1. Write the formula for transformation efficiency: TE = (Number of colonies) / (µg of DNA used).
2. Substitute the given values: TE = $9.6\times 10^6\text{colonies}/0.8\mu \text{g}$.
3. Perform the division: $9.6\times 10^6÷0.8=1.2\times 10^7$.
4. State the result with appropriate units.
5. Thus the transformation efficiency is $1.2\times 10^7$ transformants per µg of DNA.

Concept tested: Calculation of transformation efficiency

Published 10 October 2026 · How this solution was prepared and checked