Abstract: The present invention provides a method and components thereof of performing genetic modification under a drug-free environment. The method comprises the steps of generating a trapped mammalian cell library by trapper constructs (including the element of piggyBac terminal inverted repeats (TIRs)), reporter constructs, and helper constructs (including a sequence of an internal ribosomal entry site (IRES)). The present art allows: (1) to target & identify the silenced loci; (2) to separate genes with low-level expression at certain differentiation stages; (3) to evaluate the efficiency of gene targeting in the silent or repressed loci. The present invention avoids the biased gene targeting observed in the prior arts, and eliminates the needs of introducing antibiotic genes into the host genome which may lead to a potential threat of drifting antibiotic resistant genes into environment.

Abstract: The present invention provides a method and components thereof of performing genetic modification under a drug-free environment. The method comprises the steps of generating a trapped mammalian cell library by trapper constructs (including the element of piggyBac terminal inverted repeats (TIRs)), reporter constructs, and helper constructs (including a sequence of an internal ribosomal entry site (IRES)). The present art allows: (1) to target & identify the silenced loci; (2) to separate genes with low-level expression at certain differentiation stages; (3) to evaluate the efficiency of gene targeting in the silent or repressed loci. The present invention avoids the biased gene targeting observed in the prior arts, and eliminates the needs of introducing antibiotic genes into the host genome which may lead to a potential threat of drifting antibiotic resistant genes into environment.