Figure 3. Omic study of phenotype-genotype association.

The post-genome approaches to phenotype-genotype association study use similar strategies to those of genetic approaches but at an “omics” level. The top-down strategy uses a set of technologies and approaches including genomics, transcriptomics, proteomics, interactomes, and metabolomics to study the association of phenotype (a disease) and genome, transcriptome, proteome, interactome, and metabolome. Disease phenotype may be associated with multiple single-nucleotide polymorphisms (SNPs) or mutations of multiple genes, or changes in expression and/or posttranslational modification profiles of multiple proteins. The bottom-up strategy uses functional genomics, functional proteomics and functional metabolomics to test whether the findings from the top-down studies are indeed correlated to the phenotypes. These studies revealed a nonparallel relation between phenotype and genome/proteome. This also leads to current challenges in the definition of clinical phenotypes and “pure” drug targets.