 The Genotype Tissue Expression, GTX, project has been established to better understand the relationship between genes and their corresponding phenotypes. This project collects biospecimen samples from individuals with different genotypes and analyzes them for gene expression levels in order to identify the effects of genetic variations on normal physiological processes. By studying the correlation between genotype and tissue expression, researchers hope to gain insight into how genetic variations may influence drug response and disease progression. This article was authored by Judy C. Keen and Helen M. Moore.