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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 ...
Intellectual disability (ID), also known as general learning disability (in the United Kingdom [3]) and formerly mental retardation (in the United States [4]), [5][6] is a generalized neurodevelopmental disorder characterized by significant impairment in intellectual and adaptive functioning that is first apparent during childhood.
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.
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 ...
A child with Down syndrome. A prominent example of a genetically determined neurodevelopmental disorder is trisomy 21, also known as Down syndrome. This disorder usually results from an extra chromosome 21, [41] although in uncommon instances it is related to other chromosomal abnormalities such as translocation of the genetic material.
Lists. v. t. e. The following is a list of terms, used to describe disabilities or people with disabilities, which may carry negative connotations or be offensive to people with or without disabilities. Some people consider it best to use person-first language, for example "a person with a disability" rather than "a disabled person." [1]
There are a variety of disabilities affecting cognitive ability.This is a broad concept encompassing various intellectual or cognitive deficits, including intellectual disability (formerly called mental retardation), deficits too mild to properly qualify as intellectual disability, various specific conditions (such as specific learning disability), and problems acquired later in life through ...
Research has found that there is a correlation between advanced paternal age and risk of birth defects such as limb anomalies, syndromes involving multiple systems, and Down syndrome. [74] [35] [93] Recent studies have concluded that 5-9% of Down syndrome cases are due to paternal effects, but these findings are controversial. [74] [75] [35] [94]