Sequences to be inserted in yeast (i.e. GFP and 2ORE promoter) were first cloned in plasmids containing a drug resistence gene. Then the entire cassettes, which contain both the selectable marker and the coding sequence/promoter, were amplified by PCR using oligos which bring at their 5'-end 50 nucleotides that are homologous to the precise genomic region where the cassette has to be inserted. Once the PCR product has been transformed in yeast cells, it undergoes homologous recombination. Colones in which the recombination event happened in the correct way were screened by PCR as described in the figures.