What are the main distinctions between QTL and association mapping?
The main differences between QTL and association mapping are: (1) the level of resolution (in terms of distance along the DNA or chromosome), and (2) the level of generality (in terms of the number of traits that can be studied with a given set of markers). (1) QTL analyses resolve the locations of genes (or gene clusters) influencing a trait down only to the level of chromosomal segments between one to 20 cM in size (roughly one million to 20 million base pairs). Association analyses, in contrast, can provide roughly three to four orders of magnitude finer resolution on the chromosomal scale, down to the level of the actual causative gene (i.e., within thousands, or even hundreds, of base pairs). (2) QTL experiments are more general than association analyses in the sense that, in a QTL experiment, the same set of marker genotypes from a pedigree can be used to examine a wide variety of traits, the only requirements being that the trait is variable in the offspring and that some of thi
