Showing relative expression level of human epidermal growth factor in 3 different populations of Rosetta-gamiTM 2 (DE3) strain having single, double and triple copies of expression cassette. The mean value for expression level in clones containing pET28-EGF-C1 was found to be 0.61 ± 0.04. The mean value for expression level in clones containing pET28-EGF-C2 was found to be 2.36 ± 0.21 which is 3.8 folds higher as compare to their counterparts having single expression cassette. The clones containing expression vector with three expression cassettes i.e. pET28-EGF-C3 showed the mean expression level of 1.94 ± 0.154 which is 3.1 folds higher as compare to their single copy counterparts. The error bars indicate the standard error for each population.