Patent ID: 7008764

Claim:
A process for changing the expression of a nucleic acid sequence which is present endogenously in a eukaryotic cell, the method comprising (a) transfecting the cell with a vector comprising the following sequences (i) at least one sequence, which upon expression is capable of changing the expression of the nucleic acid sequence which is present endogenously in the cell, and selected from the group consisting of a heterologous expression control sequence and an amplification gene, (ii) a sequence encoding a positive selection marker, (iii) at least two target sequences for a site-specific recombinase flanking the sequences of (i) and (ii), and (iv) DNA sequences which flank the sequences of (i), (ii) and (iii) and are homologous to a nucleic acid section in the genome of the cell in order to allow a homologous recombination, (b) culturing the transfected cell under conditions under which a homologous recombination of the vector takes place, (c) isolating the cell obtained according to step (b), and (d) expressing the at least one sequence of (i) to thereby change the expression of the nucleic acid sequence which is present endogenously in the cell.