The ability to compare the gene expression of mutants against wildtypes has provided information as to which genes are important in certain functions. Mutants can be made by knocking out or inactivating genes specific for a given characteristic. Knock-out mutants can be compared with the wild type to find out what other genes are affected by genes that make the deleted characteristic work properly.  Many studies with mice knockouts have led to important findings about human diseases.  Other microarray set-ups compare differences in gene expression for two different tissue types and others compare these differences at different stages of development.  With such versatility in experimental set-up, microarrays have multiple applications in the scientific community.  For instance, things like AIDs treatment, drug therapy, forensic analysis, and cancer treatment.  All of these applications of microarray analysis could provide information needed to understand or treat the specific issue. For example, if certain genes in a cancer cell can be identified as being over or under expressed new treatments might be made available to restore these cells to there normal expression levels.

     Microarrays have functional significance in the pursuit of basic research, particularly with organisms like yeast.  Yeast not only proved to be economically important in the manufacturing of products like beer and bread but they are also scientifically important.  They serve as the accepted model for single celled eukaryotic organisms, in part because they easily grown and manipulated in the laboratory. Moreover, they are thought to share approximately 23% of there genome with humans.⁽¹⁾  Therefore, information obtained about yeast cells can progress our understanding of the human genome, metabolic pathways, and cellular responses to stimuli.  Increasing their attractiveness as experimental species, many yeast genomes, along with their complete sequences, are available on the internet for computational and experimental analysis. In fact, yeast cells are being used in laboratories worldwide.  A recent study on a rare form of Parkinson’s disease (PD) showed an excess of alpha-synuclein (aSyn) producing protein. This protein builds up in the brain and causes problems related to PD. The most fascinating thing about this experiment is that yeast cells are being used to monitor this human protein. Scientists are hoping to study the gene’s expression in normal and abnormal conditions to find out, how and when the production of the protein aSyn is made.⁽²⁾ This experiment is just one of many prime examples of why yeast models are so valuable in scientific research.

          The purpose of the present investigation is to utilize microarray analysis to characterize the differential expression pattern between a strain of wildtype  S. cerevisiae, CEN.PK 2-1C with a mutant strain, EBY.VW4000.  This mutant strain had an entire family of transmembrane protiens called hexose transporters knocked out.  Like all eukaryotic organisms, yeast depend heavily on hexoses, such as glucose,  galactose, and fructose for their most basic source of fuel.⁽³⁾ Cells require hexose transporters to carry these molecules across their lipid bilayer.  All of the twenty hexose transporters and both the two glucose signaling receptors encoded for in the yeast genome were deleted in the mutant strain. These delta hexose knockout yeast, Δhxt, and the wild type yeast, wt, were grown on glucose free-media (2% maltose) before harvesting for microarray analysis.

     It is predicted that the mutant strain will differentially express several genes related to alternative sources of energy as well as certain ones that are affected by the lack of signaling normally received from the knock-out glucose receptors.  Genes involved in the the transport and catabolic activities of disaccharides are expected to be similar in both the the wildtype and mutant because maltose, a disaccharide is the only available energy source.   However, genes involved in the transport and catabolic activities of polysaccharides and other energy rich molecules are expected to be expressed more in Δhxt than wt.   We expect to see a negative signal from receptors that monitor the presence of extracellular glucose in the wt yeast, but on the other hand expect to see no signal at all in the mutant yeast, because they lack the necessary receptors. As such, our goal is to identified those genes expressed in Δhxt yeasts which significantly deviate from the expression found in wild type yeast, even if they are not the specific genes we expect.