there is disclosed a process for in vitro synthesis and assembly of long , gene - length polynucleotides based upon assembly of multiple shorter oligonucleotides synthesized in situ on a microarray platform . specifically , there is disclosed a process for in situ synthesis of oligonucleotide fragments on a solid phase microarray platform and subsequent , “ on device ” assembly of larger polynucleotides composed of a plurality of shorter oligonucleotide fragments .