We began creating yeast strains, each with a single vector. After that, we had considered utilizing the mat a/a system for creating strain with more than one vector, but as we found our transformation method extremely efficient, we chose to execute secondary transformations on yeast cells already contain a separate vector. Parallel to these transformations, we engineered control strains that contained the empty vector, with no extra enzymatic activity, but allowed for these stains to be grown on the same selective Drop Out media. These strains were critical for creating useful control groups for our experiment design.

Further Reading:

• pESC Yeast Vectors
• Gibson Assembly