A method comprising: combining in reaction buffer (a) an initial nucleic acid molecule comprising (i) an unpaired toehold domain and (ii) a paired domain located 5' from the toehold domain that is formed by nucleotide base pairing between a displacement strand and a template strand containing the toehold domain, wherein the paired domain of the initial nucleic acid molecule comprises a molecule or modification that terminates polymerization, (b) a second nucleic acid molecule comprising (i) an unpaired toehold domain and (ii) a paired domain located 5' from the toehold domain that is formed by nucleotide base pairing between a displacement strand and a template strand containing the toehold domain, wherein the toehold domain of the second nucleic acid molecule is complementary to the displacement strand of the initial nucleic acid molecule, (c) an initial primer complementary to the unpaired toehold domain of the initial nucleic acid molecule, (d) a polymerase having strand displacement activity, and (e) deoxyribonucleotide triphosphates (dNTPs), thereby forming a reaction mixture; and incubating the reaction mixture under conditions that result in nucleic acid polymerization, strand displacement, and annealing, for a time sufficient to produce a single-stranded nucleic acid. combining in reaction buffer (a) an initial nucleic acid molecule comprising (i) an unpaired toehold domain and (ii) a paired domain located 5' from the toehold domain that is formed by nucleotide base pairing between a displacement strand and a template strand containing the toehold domain, wherein the paired domain of the initial nucleic acid molecule comprises a molecule or modification that terminates polymerization, (b) a second nucleic acid molecule comprising (i) an unpaired toehold domain and (ii) a paired domain located 5' from the toehold domain that is formed by nucleotide base pairing between a displacement strand and a template strand containing the toehold domain, wherein the toehold domain of the second nucleic acid molecule is complementary to the displacement strand of the initial nucleic acid molecule, (c) an initial primer complementary to the unpaired toehold domain of the initial nucleic acid molecule, (d) a polymerase having strand displacement activity, and (e) deoxyribonucleotide triphosphates (dNTPs), thereby forming a reaction mixture; and (a) an initial nucleic acid molecule comprising (i) an unpaired toehold domain and (ii) a paired domain located 5' from the toehold domain that is formed by nucleotide base pairing between a displacement strand and a template strand containing the toehold domain, wherein the paired domain of the initial nucleic acid molecule comprises a molecule or modification that terminates polymerization, (b) a second nucleic acid molecule comprising (i) an unpaired toehold domain and (ii) a paired domain located 5' from the toehold domain that is formed by nucleotide base pairing between a displacement strand and a template strand containing the toehold domain, wherein the toehold domain of the second nucleic acid molecule is complementary to the displacement strand of the initial nucleic acid molecule, (c) an initial primer complementary to the unpaired toehold domain of the initial nucleic acid molecule, (d) a polymerase having strand displacement activity, and (e) deoxyribonucleotide triphosphates (dNTPs), thereby forming a reaction mixture; and incubating the reaction mixture under conditions that result in nucleic acid polymerization, strand displacement, and annealing, for a time sufficient to produce a single-stranded nucleic acid.