Techniques for Gene Expression Profiling

Now that the human genome and the genomes of a growing number of important model eukaryotic organisms such as yeast and mouse have been sequenced, research emphasis in the “postgenomic” era is beginning to shift to events downstream of the whole genome. Interest is now focused on the identification and characterization of individual genes and gene networks to better understand gene function at the cell, tissue and organ levels in different states of health and disease. This new approach to studying the genome has been termed “functional genomics” because efforts are directed toward understanding the connections between the expression of individual genes or groups of genes and their unique biological functions. Although every cell in the body contains the same complement of genetic material, each is distinguished by the level and the spectrum of activation or expression of a specific set of genes. Determining which genes are active in different cells and tissues under different conditions (i.e., physiological, developmental, environmental, stress, disease, etc.) aids researchers in understanding cellular and tissue function at the molecular level. Moreover, it also allows them to relate this information to a general set of characteristics observed at the cell, tissue, and organism levels, commonly referred to as the phenotype.