The syndrome of Down, also known as trissomia of chromosome 21 is a natural and universal genetic event, being present in all the social races and classrooms. She is necessary to explain that the carriers of this syndrome are not carrying of an illness, they are only victims of one me the genetic formation, and that it lives in our way, and many are displayed, and are good for guiding that the syndrome is not a contagious pathology, what it means to say that can occur with any person at the moment of the cellular division of the still teeny embryo in the belly of the mother. All the human beings are constituted by cells and thus being, in the cellular central region, the nucleus meets that receives a structure called Chromosome, responsible by the hereditary characteristics, as the color of the skin of the eyes, of the hair, height and is distributed in pairs, being 23 inherited of mother and 23 of the father, totalizing 46 chromosomes. It happens that, in the case of the syndrome of Down, an error in the distribution and instead of 46 occurs, the cells receive 47, necessarily in the pair of chromosome 21, from there the name trissomia 21. The carriers of the repeated S.D times still are called ‘ ‘ mongolides’ ‘ , or that they suffer from ‘ ‘ mongolismo’ ‘ , due to face similarity with the people of origin of the Monglia, however, they are analyzed terms as prejudiced and aggressive, being then to the few changed by the real name syndrome of Down where John Lang Don Down homages a British doctor.