Towards marker assisted selection in livestock.

In recent years, genomic tools have become available for most livestock species and are now being used routinely to map quantitative trait loci underlying the genetic variance for numerous economically important traits. Fine-mapping methods are being devised to refine the initially coarse map positions of the quantitative trait loci to the point required for marker assisted selection and, eventually, the positional cloning of the underlying genes. Mapping information on QTL is beginning to be used to increase genetic response by enhancing genetic variance, selection accuracy, selection intensity and by reducing the generation interval. Optimal use of MAS will require the development of more robust methods for the routine genotyping of preimplantation embryos for multiple markers.