Saccharomyces cerevisiae is the most complicated eukaryotic genetic model. Most of the procedures generally used, for eukaryotic genetic engineering is grown in yeast.
a) The yeast vectors are inserted with yeast DNA of interest and are transformed into yeast cells. The plasmids are then introduced into yeast chromosome usually by homologous recombination with the occupant gene by single or double crossover.
The transformed phenotype should map to the same locus. When a gene replacement takes place by a double crossing over, the transformed cell do not possess vector DNA. But if a single crossing over occurs, the complete vector is the portion of the linear chromosome of Saccharomyces cerevisiae.
b) In, Saccharomyces cerevisiae and other yeasts, a variety of autonomously replicating plasmids are used. The integration of transforming DNA is done by homology. If the transforming gene is inserted ectopically i.e. by another location, the transformed phenotype should map to a different locus than that of the auxotroph.