Ubiquity
Although there are so many negative effects related to genes that are antagonistically pleiotropic, it is still present among most forms of life. Indeed, pleiotropy is one of the most common traits possessed by genes overall. In addition to that, pleiotropy is under strong stabilizing selection. In one experiment with mice and the morphology of the mandible, 1/5 of the loci had effects of pleiotropy for the entire mandible. One other example was in the Russian biologist Dmitry K. Belyaev's study on the domestication of the fox. In Dmitry K. Belyaev's farm-fox experiment, wild foxes were bred for docile behavior alone. After 40 generations, other physiological changes had surfaced including shortened tails, floppy ears, a white star in the forehead, rolled tails, shorter legs. Since the only thing being selected for was behavior, this leads scientists to believe that these secondary characteristics were controlled by the same gene or genes as docile behavior.
Read more about this topic: Antagonistic Pleiotropy Hypothesis