Editing Protein engineering (section)

====Error prone PCR====
Error prone PCR utilizes the fact that Taq DNA polymerase lacks 3' to 5' exonuclease activity. This results in an error rate of 0.001–0.002% per nucleotide per replication. This method begins with choosing the gene, or the area within a gene, one wishes to mutate. Next, the extent of error required is calculated based upon the type and extent of activity one wishes to generate. This extent of error determines the error prone PCR strategy to be employed. Following PCR, the genes are cloned into a plasmid and introduced to competent cell systems. These cells are then screened for desired traits. Plasmids are then isolated for colonies which show improved traits, and are then used as templates the next round of mutagenesis. Error prone PCR shows biases for certain mutations relative to others. Such as biases for transitions over transversions.<ref name=PoluriBook/>{{page needed|date=May 2017}}

Rates of error in PCR can be increased in the following ways:<ref name=PoluriBook/>{{page needed|date=May 2017}}
# Increase concentration of magnesium chloride, which stabilizes non complementary base pairing.
# Add manganese chloride to reduce base pair specificity. 
# Increased and unbalanced addition of dNTPs.
# Addition of base analogs like dITP, 8 oxo-dGTP, and dPTP.
# Increase concentration of Taq polymerase.
# Increase extension time.
# Increase cycle time.
# Use less accurate Taq polymerase.
Also see [[polymerase chain reaction]] for more information.