An automated system for the synthesis of a dsDNA molecule according to provided sequence information, comprising: an assembly unit for assembling the dsDNA molecule according to the provided sequence information, wherein the assembly unit comprises or is connected to vessels containing nucleotide derivative or nucleoside phosphoramidites and containing components for transporting reagents within the system and for executing steps in an automated method for assembling the dsDNA molecule through multiple levels of biological assembly, wherein the multiple levels of biological assembly comprise 1) the synthesis of a plurality of oligonucleotides by linking nucleotide derivatives or nucleoside phosphoramidites, and 2) the assembly of one or more dsDNA molecule(s) by joining the plurality of oligonucleotides; wherein no human intervention occurs after the method is initiated until the method is completed; and wherein the assembly unit further comprises software programming instructions which direct manipulations of the parts of the assembly unit to synthesize the plurality of oligonucleotides from nucleotide derivative or nucleoside phosphoramidites according to the sequence information and assemble the oligonucleotides into the dsDNA molecule in the automated method; the automated method comprising performing on the plurality of oligonucleotides a step of PCR amplification in a first reaction zone of a reaction container, a step of error correction on the PCR-amplified oligonucleotides in a second reaction zone of a reaction container, and a second PCR step in a third reaction zone of a reaction container; wherein the error correction is performed using a combination of a member of the CEL nuclease family of mismatch-specific nucleases and exonuclease III; wherein the assembly unit employs robotics to transport samples between reaction zones such that the automated method can be conducted in one reaction container; wherein the oligonucleotides are fragments of the dsDNA molecule or variants thereof; and further wherein the assembly unit performs assembly in an automated method that comprises the synthesis of the dsDNA molecule that is greater than 100 bp by joining said oligonucleotides. an assembly unit for assembling the dsDNA molecule according to the provided sequence information, wherein the assembly unit comprises or is connected to vessels containing nucleotide derivative or nucleoside phosphoramidites and containing components for transporting reagents within the system and for executing steps in an automated method for assembling the dsDNA molecule through multiple levels of biological assembly, wherein the multiple levels of biological assembly comprise 1) the synthesis of a plurality of oligonucleotides by linking nucleotide derivatives or nucleoside phosphoramidites, and 2) the assembly of one or more dsDNA molecule(s) by joining the plurality of oligonucleotides; wherein no human intervention occurs after the method is initiated until the method is completed; and wherein the assembly unit further comprises software programming instructions which direct manipulations of the parts of the assembly unit to synthesize the plurality of oligonucleotides from nucleotide derivative or nucleoside phosphoramidites according to the sequence information and assemble the oligonucleotides into the dsDNA molecule in the automated method; the automated method comprising performing on the plurality of oligonucleotides a step of PCR amplification in a first reaction zone of a reaction container, a step of error correction on the PCR-amplified oligonucleotides in a second reaction zone of a reaction container, and a second PCR step in a third reaction zone of a reaction container; wherein the error correction is performed using a combination of a member of the CEL nuclease family of mismatch-specific nucleases and exonuclease III; wherein the assembly unit employs robotics to transport samples between reaction zones such that the automated method can be conducted in one reaction container; wherein the oligonucleotides are fragments of the dsDNA molecule or variants thereof; and further wherein the assembly unit performs assembly in an automated method that comprises the synthesis of the dsDNA molecule that is greater than 100 bp by joining said oligonucleotides.