Procedures and vectors are provided for the specific alteration of particular genetic loci in eukaryotic cells. One procedure utilizes fluorescence-probe-in-cell (FPIC) gene targeting DNA vectors for the purpose of creating and identifying cells which have vector sequences integrated into the host cell genome via site-specific homologous recombination. The procedure also utilizes sequences encoding in vivo detectable markers for the identification of cells which have exogenous vector sequences integrated into the genome of the host cell, either via site-specific homologous recombination or nonhomologous recombination or insertion. In addition, cells modified using a FPIC vector, and organisms generated from such cells, are provided.
