Abstract: Using chromosome DNA of S.thermophilus as template.Thymidylate sythase(thyA)gene was amplified by PCR with ExTaq DNA polymerase,and purified by purification kit.Subsequently,the PCR production of thyA gene was cloned into the pMD-18T,transformed into DH5αThe recombination plasmid containing thyA gene was selected and identified by restriction enzyme analysis and by PCR amplification and sequence.The results showed that the whole thyA gene is cloned already(about 900bp).Sequence analysis showed that the thyA gene displays 99.9% nucleotide identities with the published sequences.The thyA gene offers a good foundation for the shuttle vector construction by thymidylate synthase(thyA)gene as a selective pressure.

Key words: thyA gene, cloning, sequence analysis