Question+Two

= What animals can be used for xenotransplantation? =

====Non-human primates were first considered as a potential organ donor for xenotransplantation as they are the closest relatives to humans. Chimpanzees were originally considered to be the best option as their organs are relatively the same size and they have good blood type compatibility with humans. However, chimpanzees are an endangered species, this thought was quickly abandoned.====

====Baboons were next to be considered, but they are not as good a donor as chimpanzees as they have a smaller body size, the infrequency of blood group O, their long gestation period, and the usually small amount of children they produce. A major problem with using primates as organ donors is the increased risk of disease transmission, as they are closely related to humans.====

====Currently, the best organ donor is considered to be the pig. There is less risk of cross-species disease transmission as they are distanced from humans in the phylogenetic tree. Their organs are similar in size to humans', and new infectious agents are less likely as they have been in close contact with humans for many generations. They are also more readily available as pigs are born in large litters which are easy to rear in pathogen-free conditions.====