DNA marker technology: a revolution in animal genetics.

The development of DNA-based markers has had a revolutionary impact on gene mapping and, more generally, on all of animal and plant genetics. With DNA-based markers, it is theoretically possible to exploit the entire diversity in DNA sequence that exists in any cross. For this reason, high resolution genetic maps are being developed at an unprecedented speed. The most commonly used DNA-based markers include those based on a cloned and (usually) sequenced DNA fragment and other, more random, assays for genetic polymorphism that can be grouped under the heading of fingerprint markers. The advantages and disadvantages of the various marker types are discussed, along with their application to the reference chicken genetic linkage maps and to the search for quantitative trait loci (QTL). The prospects for the use of DNA-based markers in marker-assisted selection are considered, along with likely future trends in poultry gene mapping. Further development of both physical and linkage genome maps of the chicken will allow animal scientists to more efficiently detect and characterize QTL and will provide them access to the wealth of genetic information that is being generated about the human genome and the genomes of model species, such as the mouse and Drosophila.