This invention provides a method for combining overlapping DNA molecules comprising: (a) providing first and second DNA fragments, the first having a region homologous to a region in the second; (b) tagging the first DNA fragment with a selectable marker; (c) cloning the first DNA sequence into a retrieval vector to form a DNA-vector complex; (d) linearizing the DNA-vector complex; and (e) inserting the first DNA fragment from the DNA-vector complex into the second DNA fragment using homologous recombination to form a combined DNA molecule; and (f) removing the selectable marker, thereby generating a combined DNA molecule. The invention further provides a vector for retrieving and inserting a selected DNA molecule into a target DNA molecule.