2.1. Quantitative trait loci influencing blood pressure
The principal strategy in the rat for the search of genes involved in the development of hypertension has been the identification of QTLs responsible for blood pressure regulation by genome-wide scanning [15] and [21]. The difficulties in identifying QTLs include epistasis, and a limited statistical power due to the number of hypotheses being tested. Moreover, any single QTL is responsible for only a fraction of the phenotypic variation and thus the phenotype–genotype correlation is low. Improvements in genomic resources and statistical analysis have led to the identification of a large number of QTLs. However, despite the numerous complex traits that have been analysed by genome-wide linkage studies, few of the underlying genes have been identified [22].