Validation of genome-wide association studies (GWAS) results.

Validation of the results of genome-wide association studies or genomic selection studies is an essential component of the experimental program. Validation allows users to quantify the benefit of applying gene tests or genomic prediction, relative to the costs of implementing the program. Further, if implemented, an appropriate weight in a selection index can only be derived if estimates of the accuracy of genomic predictions are available. In this chapter the reasons for validation are explored, and a range of commonly encountered scenarios described. General principles are stated, and options for performing validation discussed. Designs for validation are heavily dependent on the availability of phenotyped animals, and also on the pedigree structures that characterize the breeding program. Consequently, there is no single plan that is always applicable, and a custom plan often must be developed.