ABSTRACT
Linked marker tests are based on the cosegregation of DNA markers and phenotypes within families. Thus, the linkage phase (the association between the markers being tested and the gene affecting the phenotypes) must be established within each family in which the markers are to be used for selection. Consequently, DNA tests must be performed on progeny with phenotypes within each family. This is the primary factor limiting the application of linked markers. Consequently, they are best suited to within-herd use by large breeding companies. Linked markers have the advantage of being the easiest and least expensive to develop. Most published QTL are currently defined by linked markers. Over time, many of these will be converted to association tests, and eventually, to functional tests.
