Purified PCR products were cloned into a pCR2.1-TOPO vector (Invitrogen) according to manufacturer's instructions. The vector was then used to transform the competent Escherichia coli strain DH5a by electroporation. Positive transformants were identified by blue-white screening, and eight colonies were selected for DNA sequencing of the construct using the M13 forward and reverse primers according to the manufacturer's instructions. Sequencing reactions were performed as described above.