Animal 3: Cloned Pigs

If all pigs were as good at spelling as Wilbur, you might be a li­ttle more stoked about this particular selection. But while pigs can't spell -- it was Charlotte's doing, after all -- they do make some pretty mean bacon. If meat isn't your thing, cloned pigs are also sought after because of the suitability of their organs for human transplantation.

Transferring cells, tissues or organs from one species to another is known as xenotransplantation and is viewed as a potential solution to the shortage of organs and cells for lifesaving transplants. By tweaking the genetic makeup of pigs, a biopharmaceutical company named PPL Therapeutics has fine-tuned the animals' DNA so some of their organs and cells can be used successfully in people. These genetically altered pigs can be cloned to mass-generate things like insulin-producing cells for the treatment of type 1 diabetes and organs like hearts and kidneys [source: PPL Therapeutics, Inc.].

According to the European Food Safety Authority (EFSA), which recently conducted a study on the safety of products obtained from cloned animals and their offspring for consumption, there are already at least 500 cloned pigs in existence worldwide [source: EFSA]. And like goats, porcine foodstuffs also got the green light from the FDA, so it's likely that the number of pigs being cloned will increase. As advancements continue to be made with the treatment of human disease and xenotransplantation, pigs should continue to stake out a pretty prominent spot on the list of most cloned animals.