Genome-wide knockdown studies are an example of the reverse genetics made possible by the acquisition of whole genome sequences, and the advent of genomics and gene-silencing technologies, mainly siRNA and deletion mapping.  Genome-wide knockdown studies involve systematic knockdown or deletion of genes or segments of the genome.  This is generally done in prokaryotes or in a tissue culture environment due to the massive number of knockdowns that must be performed.  After the systematic knockout is completed (and possibly confirmed by mRNA expression analysis), the phenotypic results of the knockdown/knockout can be observed.  Observation parameters can be selected to target a highly specific phenotype.  The resulting dataset is then queried for samples which exhibit phenotypes matching the disease in question – the gene(s) knocked down/out in said samples can then be considered candidate disease genes for the individual in question.