Resolution of complex integration patterns to obtain single copy

Abstract

The present invention provides methods for producing a transgenic cell having a stably integrated, single copy of an exogenous polynucleotide sequence. The method, which resolves repeated insertions of the introduced polynucleotide sequence into a single copy, involves introducing into a genetic locus of a cell a polynucleotide sequence flanked on each end by a recombination site. The recombination sites are oriented such that contact with a recombinase would not result in deletion of the polynucleotide sequence from the construct. The multiple, tandem copies of the introduced polynucleotide locus are then contacted with a recombinase that catalyzes recombination among the recombination sites. As a result of this method, the multiple, tandem copies are resolved to a single copy.