Abstract: The method of synthesizing a segment of DNA, typically a gene, of predetermined structure which comprises synthesizing a first pair of oligonucleotides having ends complementary to the ends enzymatically made at a restriction site on a standard plasmid vector, said first pair of oligonucleotides including adjacent their ends portions of said predetermined structure and each having a pair of restriction sites internal to said portions of predetermined structure which restriction sites are unique to the enzyme and not present in the plasmid vector, cloning said first pair of oligonucleotides into said standard plasmid vector, and amplifying said plasmid vector in vivo to recover plasmid vector containing said first pair of oligonucleotides, repeating said method with a second pair of ologonucleotides, containing portions of predetermined structure which are adjacent to the portions present in the first pair of oligonucleotides, and continuing said repetition until all of said segment of predetermined structure