Daniel Gibson and his colleagues at the J.Craig Venter Institute, USA have developed a method for Assembling Dna Molecules up to several hundred kilo-bases in  a Test Tube. Their study is published in Nature Methods 6, 343 - 345 (2009). According to the method described by them, DNA molecules are assembled in a isothermal, single-reaction process with the concerted action of a 5' -  exonuclease, a DNA polymerase and a DNA ligase. A single-step process makes it faster and fully controllable. This will further allow in vitro Assembly of genes, entire genetic pathways, or even small genomes from natural or Synthetic Dna.

P.S. : Daniel Gibson's group previously assembled the entire genome (583 kilo-base-pair) of Mycoplasma genitalium using synthetic DNA. The final steps of DNA assembling could be accomplished in a yeast cell and it is difficult as the foreign DNA maybe toxic to the yeast.