Many taste phenotypes are measured using a continuous quantitative scale (e.g. volume of solution consumed, preference score or lick rate) and thus are considered quantitative traits. Genes with allelic variants that underlie variation of quantitative traits reside in chromosomal regions named quantitative trait loci (QTL). Defining these chromosomal regions through genetic linkage analysis is called QTL mapping. QTL mapping helps to identify DNA sequences of genes in the QTL regions and to find genes that are responsible for phenotypical variation. Because this approach to identify genes is based on a chromosomal position of a phenotypical locus, it is called positional cloning. Quantitative traits that depend on multiple genetic and environmental factors are considered complex traits. There is strong evidence that sweet taste preference is a complex trait.
