Methods for high fidelity production of long nucleic acid molecules with error control

A method for synthesizing a nucleic acid having a desired sequence and length, the method comprising:

• a) providing a solid support having an immobilized nucleic acid, wherein the solid support is a bead or particle;
• b) performing a nucleic acid addition reaction to elongate the immobilized nucleic acid by adding a nucleotide or an oligonucleotide to the immobilized nucleic acid;
• c) after the nucleic acid addition reaction, determining whether the nucleotide or the oligonucleotide is added to the immobilized nucleic acid by detecting whether there is an increase in electrophoretic force applied to the solid support when an electric field and a magnetic field gradient are applied to the solid support, wherein the increase in electrophoretic force applied to the solid support is caused by adding the nucleotide or the oligonucleotide to the immobilized nucleic acid;
• d) repeating steps b) and c) if the nucleotide or the oligonucleotide is not added to the immobilized nucleic acid;
• and
• e) synthesizing the nucleic acid having a desired sequence and length by repeating steps b) through d).