The University of Illinois' Huimin Zhao and his colleagues report on their new DNA assembler method in Nucleic Acids Research. Needing only simple DNA preparation and a one-step yeast transformation, this in vivo process can assemble an entire biochemical pathway of Saccharomyces cerevisiae in a single step by taking advantage of homologous recombination. "Assembling genes into a biochemical pathway using a DNA assembler is similar to building a toy train.