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Trisomy 21. Down syndrome (also known by the karyotype 47,XX,+21 for females and 47,XY,+21 for males) [98] is mostly caused by a failure of the 21st chromosome to separate during egg or sperm development, known as nondisjunction. [91] As a result, a sperm or egg cell is produced with an extra copy of chromosome 21; this cell thus has 24 ...
John Langdon Down. John Langdon Haydon Down (18 November 1828 – 7 October 1896) was a British physician best known for his description of the genetic condition now known as Down syndrome, which he originally classified in 1862. He is also noted for his work in social medicine and as a pioneer in the care of mentally disabled patients.
Genetics of Down syndrome. Down syndrome is a chromosomal abnormality characterized by the presence of an extra copy of genetic material on chromosome 21, either in whole (trisomy 21) or part (such as due to translocations). The effects of the extra copy varies greatly from individual to individual, depending on the extent of the extra copy ...
The average IQ of a young adult with Down syndrome is 50, equivalent to the mental age of an 8- or 9-year-old child, but this number varies widely. [3] At the same time, they enjoy a rich social and emotional awareness. [4] Down syndrome is the most common chromosome abnormality in humans, [3] occurring in about one per 1000 babies born each ...
World Down Syndrome Day (WDSD) is marked each year on March 21, [1] beginning in 2007. The 21st day of March (the 3rd month of the year) was selected to signify the uniqueness of the triplication (trisomy) of the 21st chromosome which causes Down syndrome. The General Assembly of the United Nations has decided to observe it each year since 2012.
23 (2019) [1] Jordan's syndrome (JS) or PPP2R5D-related intellectual disability is a rare autosomal dominant neurodevelopmental disorder caused by de novo mutations in the PPP2R5D gene. [2] It is characterized by hypotonia, intellectual disability, and macrocephaly. [3] Children with JS may also have epilepsy or meet criteria for diagnosis with ...
Patau syndrome. Patau syndrome is a syndrome caused by a chromosomal abnormality, in which some or all of the cells of the body contain extra genetic material from chromosome 13. The extra genetic material disrupts normal development, causing multiple and complex organ defects. This can occur either because each cell contains a full extra copy ...
Locked-in syndrome (LIS), also known as pseudocoma, is a condition in which a patient is aware but cannot move or communicate verbally due to complete paralysis of nearly all voluntary muscles in the body except for vertical eye movements and blinking. [3] The individual is conscious and sufficiently intact cognitively to be able to communicate ...