Classical QTL analysis has associated individual differences in gene sequence (or in other genetic markers, such as microsatellites) with differences in the phenotype being mapped. A recent development in rodent QTL mapping has been development of expression QTL (eQTL) mapping. eQTLs are DNA regions that differ not in their gene sequence, but in the level to which the gene becomes active (i.e., is expressed) in individuals differing with respect to certain alcohol-related traits. This information can be gathered from microarray experiments that measure the levels of individual mRNAs. These additional eQTLs greatly expand the pool of potentially informative genes.
