Recently the Boone group published a short report concerning the generation of systematic gene deletion for another strain of yeast: Genotype to phenotype: a complex problem.
Its amazing how much work went into this short reports, but this is the first study to show that genes required for growth can be significantly different between closely related strains of the same species. The article from the Boone lab stems from the observation that the genes required for growth in one strain of yeast can be dramatically different from another strain. This strain-to-strain difference is surprising and suggests that separate pathways are required for growth among very similar strains through the evolution of mutations which can buffer these essential pathways. The lessons learned here will likely be reflected in humans where individual variation can contribute to dependence on different sets of pathways and genes. An observation which has relevance to how people think about drug discovery and personalized medicine.