Calculating Transformation Efficiency for Human cDNA Library Construction

1. Problem 36_1.1 You are interested in constructing a human cDNA library (genome size of 7.9x108bp) and begin by inserting cDNA fragments (average insert size of 4.3 kb) into your plasmid. You then start your transformation reaction by pipetting 50 ml of a 2.5 mg/ml solution of the plasmid DNA into 4 ml of competent E. coli cells. After transformation is completed, you take 10 ml of the competent cell mixture and plate it onto agar plates containing ampicillin. After incubation of the plates overnight at 37 0C, you count 2300 colonies on the plate. What is the transformation efficiency of your transformation reaction?

2. Problem 36_1.1 You are interested in constructing a human cDNA library (genome size of 7.9x108bp) and begin by inserting cDNA fragments (average insert size of 4.3 kb) into your plasmid. You then start your transformation reaction by pipetting 50 ml of a 2.5 mg/ml solution of the plasmid DNA into 4 ml of competent E. coli cells. After transformation is completed, you take 10 ml of the competent cell mixture and plate it onto agar plates containing ampicillin. After incubation of the plates overnight at 37 0C, you count 2300 colonies on the plate. What is the transformation efficiency of your transformation reaction? 2.5 µg/ml x (50 µL/1000 µL) = 0.125 µg DNA added to cells 0.125 µg x (10 µL/4000 µL) = 3.12 x 10-4 µg DNA plated (2.3x103 colonies)/(3.2x10-4 µg) = 7.36 x 106 transformants per µg DNA