1 ) A method for producing a vector having a desired nucleic acid insert from a sample comprising a plurality of vectors, the method comprising: generating first and second extension products from first and second primers, wherein the first and second primers anneal to complementary strands of the vector in the sample having the desired nucleic acid insert, wherein one or both of the first or second primers contain a nucleic acid sequence found in the desired nucleic acid insert or its complement, wherein the first and second extension products are capable of annealing to each other at the terminal ends, and wherein the nucleic acids of the first and second extension products together comprise a sequence for replication in a host and the desired nucleic acid insert; optionally repeating the step of generating first and second extension products; and combining and annealing the first and second extension products to form a partially double-stranded, replication-competent vector.