Patent ID: 8207318

Claim:
A reaction mixture comprising: (a) a first double-stranded DNA molecule which comprises a promoter, (b) a second double-stranded DNA molecule, and (c) a recombinant nucleic acid molecule formed from the first double-stranded DNA molecule and the second double-stranded DNA molecule, wherein at least one end of at least one strand of the first double-stranded DNA molecule is topoisomerase-charged, wherein at least one end of at least one strand of the second double-stranded DNA molecule is topoisomerase-charged, and wherein the topoisomerase-charged ends of the first double-stranded DNA molecule and the second double-stranded DNA molecule are capable of hybridizing to each other such that in the recombinant nucleic acid molecule formed from the first double-stranded DNA molecule and the second double-stranded DNA molecule each strand of the first double-stranded DNA molecule is covalently linked to each strand of the second double-stranded DNA molecule and the recombinant nucleic acid molecule-does not contain a nick in either strand at the position where the first and second nucleic acid molecules are joined.