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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 ...
Neurodevelopmental disorders are a group of mental conditions affecting the development of the nervous system, which includes the brain and spinal cord.According to the American Psychiatric Association Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, published in 2013, these conditions generally appear in early childhood, usually before children start school, and can ...
The obsolete medical terms Mongolian idiocy and Mongolism referred to a specific type of mental deficiency, associated with the genetic disorder now known as Down syndrome. The obsolete term for a person with this syndrome was called a Mongolian idiot. In the 21st century, these terms are no longer used as medical terminology, deemed an ...
Down syndrome is a genetic condition in which people are born with an extra copy of chromosome 21. This extra copy affects the development of the body and brain, causing a range of physical and mental impairments for the individual. Fragile X syndrome, most frequent among males, is thought to cause autism and intellectual disability.
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 term idiot savant (French for "learned idiot") was first used to describe the condition in 1887 [24] by John Langdon Down, who is known for his description of Down syndrome. Down described approximately ten cases of youth he had known with unusual mental powers, like "verbal adhesion" (eg. memorizing books read once), photographic memory ...
The scientific study of the causes of developmental disorders involves many theories. Some of the major differences between these theories involves whether environment disrupts normal development, if abnormalities are pre-determined, or if they are products of human evolutionary history which become disorders in modern environments (see evolutionary psychiatry). [5]