After the transformations of the plasmid pUC19 or the lacZ gene
fragment into the bacteria and selection of mutants, DNA was extracted
from the white colonies or mutants and the extracted DNA samples
were sequenced at the First Base Laboratories Sdn. Bhd., Malaysia. The
specific primers used to cover the promoter and complete the lacZ
gene sequence were LacZF1 primer (5′- GCT TGT CTG TAA GCG GAT
GC -3′) and LacZR1 primer (5′ -GCG GGC AGT GAG CGC AAC GC -3′).
The DNA sequencing result was compared with the original pUC19 sequence
for analysis of the base changes. The mutation frequency of a