Targeting of Genes to Specific Sites in the Mammalian Genome

Gene targeting — the homologous recombination of DNA sequences residing in the chromosome with newly introduced DNA sequences — provides the means for systematically altering the mammalian genome (Lin et al. 1985; Smithies et al. 1985; Thomas et al. 1986). A desired alteration would first be introduced into a cloned DNA sequence, and gene targeting would then transfer the alteration into the genome. Gene targeting should be equally effective for correcting or mutating the desired chromosomal locus.