The chimpanzee that confirmed the abnormality is an individual with an abnormality on chromosome 22 of chimpanzee (trisomy: an abnormality with three chromosomes, which is usually two), and chromosome 2 of a large human monkey corresponds to chromosome 3 of humans. A case corresponding to human chromosome 22 trisomy.

　Human chromosome 21 trisomy causes Down's syndrome, which is reported to occur in about 600 in 1 people, and is a congenital disease that often causes delays in physical development and cognitive development, and physical disorders.In non-human primates, the world's first case of Down's syndrome-like chimpanzee was discovered in the United States in 1969.This is an example of a trisomy of chimpanzee chromosome 22, and developmental retardation and congenital heart disease were confirmed in this chimpanzee.Since then, similar trisomy 22 has been reported in gorillas and orangutans.

　The research group identified trisomy 22 of the female chimpanzee, Kanako, bred at the Wildlife Research Center Kumamoto Sanctuary.Kanako has developmental delay and congenital cataracts, nystagmus with unintentional eye movements, strabismus, keratoconus (keratoconus degeneration), congenital heart disease, and tooth defects.Both are characteristic symptoms of Down's syndrome in humans, and are the second reported individual chimpanzee chromosome 22 trisomy in the world.

　The research team said, "If the similarities and differences with Down's syndrome in humans are clarified by observing future behavior, it will lead to a better understanding of Down's syndrome." Is sent.