Traditional breeding schemes and marker assisted selection based on phenotypes and so
called quantitative trait loci has been very successfully used for incremental genetic
improvement associated with the gradual modification of the genome. However, due to the
complexity of the genome these breeding schemes involve trade-offs with not only the
introduction of characteristics selected for but often undesirable alleles associated with
other, non-selected traits. In a way, transgenic technology which allows for a more direct
approach with the potential to enhance existing characteristics at unprecedented magnitude
and speed can be seen as an extension of these more traditional efforts to modify livestock
genomes