The Transposons-based system. A. General principle of transposon-based system; the transposon-based system includes two parts: a transposon vector containing DNA sequence that is flanked by inverted repeat/direct terminal repeat (IR/DR) sequences, and the transposase enzyme responsible for excision and reintegration of the transposon under the control of a promoter; when transposon vector and transposase are present together, a “cut-and-paste” transposition reaction occurs; the transposon is excised from its original location and re-integrated to a new location within the genome. SB and PB are two different transposases. SB transposase inserts a transposon into a TA dinucleotide base pair sequences, PB transposase inserts a transposon into a TTAA dinucleotide base pair sequences. B. Transposon-based somatic cell transgenic mouse system; to generate the somatic cell transgenic mouse model, two plasmids are injected together into mice to cause mutations in specifically targeted cells; the transposon insertion sites are detected using PCR screening. C. Transposon-based germ line cell transgenic mouse system; to generate the germ line cell transgenic mouse model, two mouse strains are required: one strain carries the transposons vector gene, and the other carries the transposase gene; these two mouse strains are bred to generate the F1 generation of double transgenic mice; F1 males are crossed with wild-type females to segregate the different insertion events in their sperm cells, generating F2 in the process; then the F2 mice are screened to select the ones with the desired mutant allele, and these mice are crossed together to generate F3 homozygous mice.