(a) Preparation of each gene expression cassette using OE-PCR. Promoters (Px, Px+1), genes (Gx, Gx+1), and terminators (Tx, Tx+1) are individually PCR-amplified and joined together by OE-PCR. The resulting two cassettes are fused through the in vivo homologous recombination (HR) process. To generate an overlap of approximately 50 bp, the reverse primer used to amplify Tx contains a sequence of the first 20-25 nucleotides of Px+1, and the forward primer used to amplify Px+1 contains a sequence of the last 20-25 nucleotides of Tx. (b) One-step method for assembly of a biochemical pathway using in vivo homologous recombination (HR) in S. cerevisiae.