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Figure 9 | BMC Molecular Biology

Figure 9

From: Homologous illegitimate random integration of foreign DNA into the X chromosome of a transgenic mouse line

Figure 9

Random integration mechanism of foreign DNA by homologous illegitimate random integration and course of fad2 inserted into the X chromosome. (A) Identical foreign DNA injected into the nucleus of a eukaryotic cell is circularised and randomly cleaved by the endogenous restriction enzyme(s). It generates tandem concatemers by homologous recombination (steps 1-3, adapted from reference [2]). The concatemers are inserted into the host genome, mediated by homologous illegitimate random integration (HIRI), which depends on several identical nucleotide sequences (in red or blue) in the AT-rich domains on both sides, which serve as anchors for the two DNAs. Consequently, a host DNA region is replaced by the foreign DNA. During DNA replication, the repair mechanism of the cell induces foreign DNA integration into the host genome (steps 4-5). (B) Fad2 transgenic concatemers consist of a ≥322-bp complementary DNA and multiple copies inserted in a head-to-tail array by homologous recombination. During the HIRI process, 5'-TGT-3' and 5'-TTAATAG-3' (capital letters in blue) in the AT-rich domain, which exist in both foreign DNA and the X chromosome, mediate the illegitimate recombination of the transgene and the X chromosome as the homologous arms. When the homologous foreign DNA is inserted into the X chromosome, all of the 45,556 target nucleotides on the X chromosome are replaced by the foreign DNA.

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