7楼: Originally posted by gyesang at 2013-12-10 15:00:37
BL21(DE3)

F– ompT gal dcm lon hsdSB(rB- mB-) λ(DE3 )

    an E. coli B strain with DE3, a λ prophage carrying the T7 RNA polymerase gene and lacIq
    Transformed plasmids containing T7 pro ...

2楼: Originally posted by gyesang at 2013-12-09 11:30:35
pET系列载体的基因诱导表达是受T7 RNA polymerase和LacI阻遏双重控制的，lacI缺失两个碱基，那会造成LacI基因的移码突变的，LacI就不能阻遏T7 RNA polymerase的表达，从而起不到诱导表达的作用