Scientists Document Second Case of Trisomy 22 in Chimps (“Chimpanzee Down Syndrome”)

Japanese researchers have confirmed the second case known to science of a chimpanzee born with trisomy 22, a chromosomal defect similar to that of Down syndrome (or trisomy 21) in humans. The report on Kanako (photo), a 24-year-old female chimp born into captivity, was led by Dr. Satoshi Hirata of Kyoto University in Japan, and appeared online on February 21, 2017 in the journal Primates, published by Springer. The article is titled “Chimpanzee Down Syndrome: A Case Study of Trisomy 22 in a Captive Chimpanzee.” The authors also describe their attempts to improve the quality of life of this chimpanzee, through providing and managing opportunities for normal social interaction. Such efforts are seen as key in caring for disabled chimpanzees in captivity. Human cells normally contain 23 pairs of chromosomes, for a total of 46. Down syndrome occurs when a person’s cells contain a third copy of chromosome 21 (also known as trisomy 21). In turn, apes have 24 pairs of chromosomes, for a total of 48. Trisomy 22 is diagnosed when the cells of apes such as chimpanzees, gorillas, or orangutans contain a third copy of chromosome 22. The first confirmed case of a chimpanzee with trisomy 22 was documented in 1969. The chimpanzee described nearly five decades ago died before its second birthday. This means that Kanako is the longest-living chimp with this chromosomal disorder that scientists are aware of. Kanako was born in captivity in 1992, at a facility which was transferred to Kyoto University in 2011 and renamed as Kumamoto Sanctuary, Wildlife Research Centre. She experienced stunted growth from an early age, suffers from a congenital heart disease and has underdeveloped teeth. Kanako developed cataracts before the age of one, and became blind by the age of seven.
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