A second case of Trisomy defect has been marked in a Japanese chimp, which is a defect of 21st chromosome in humans. The researchers of Kyoto University have successfully identified the genetic defect, whose findings have been published in the Springer journal Primates. In case of chimps, the trisomy defect is seen in the 22nd chromosome, which has a triplet copy.
Reference link: http://www.springer.com/gp/about-springer/media/research-news/researchers-document-second-case-of–down-syndrome–in-chimps/12080886