Food Biochemistry and Food Processing (2 edition)

BLBS102-c07 BLBS102-Simpson March 21, 2012 11:12 Trim: 276mm X 219mm Printer Name: Yet to Come

7 Biocatalysis, Enzyme Engineering and Biotechnology 149

Figure 7.18.PCR oligonucleotide-directed mutagenesis. Two sets of primers are used for the amplification of the double-stranded plasmid

DNA. The primers are positioned as shown and only one contains the desired base change. After the initial PCR step, the amplified PCR

products are mixed together, denatured and renatured to form, along with the original amplified linear DNA, nicked circular plasmids

containing the mutations. Upon transformation intoE. coli, the nicked are repaired by host cell enzymes and the circular plasmids can be

maintained.