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- 200 µl transformation solution (CaCl₂) added to E. coli
- 20 µl plasmid DNA added to the competent cells (DNA plasmid concentration 12.5 µg/ml)
- 600 µl LB broth added following the heat shock
- 100 µl of the transformation mixture plated on each LB/LB+amp plate
- Average of 185 colonies grown on each LB+amp plate after 24 hours
- Lawn of bacteria on LB plate (no ampicillin) after 24 hours

a. Calculate the transformation efficiency of this experiment in units of transformants µg⁻¹ plasmid DNA.

Answer :

Final answer:

The transformation efficiency is calculated by taking the average number of colonies (185), adjusting for the fraction of the transformation mixture that was plated, and dividing by the amount of plasmid DNA used in the transformation. The calculated transformation efficiency is 1,666 transformants/µg of plasmid DNA.

Explanation:

Calculate the Transformation Efficiency:

To calculate the transformation efficiency, follow these steps:


  2. First, determine the total number of transformants, which is the average number of colonies grown on the LB+amp plates. In this case, there are 185 colonies.

  4. Next, calculate the amount of plasmid DNA used in the transformation. The concentration is given as 12.5 µg/ml, so for 20 µl, the amount is (12.5 µg/ml) × (20 µl) = 0.25 µg.

  6. Since 100 µl of the transformation mixture was plated, and the transformation mixture contains 220 µl total (200 µl CaCl2 + 20 µl DNA), the fraction plated is 100 µl/220 µl. Therefore, you must account for this by dividing the number of colonies by this fraction.

  8. Finally, the transformation efficiency is calculated by dividing the number of transformants by the amount of DNA (in µg) used in the transformation. So, the transformation efficiency = (185 / (100/220)) / 0.25 µg = 1,666 transformants/µg.

In this experiment, the transformation efficiency is 1,666 transformants/µg of plasmid DNA.

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