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Down syndrome or Down's syndrome, [12] also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. [3] It is usually associated with developmental delays, mild to moderate intellectual disability , and characteristic physical features.
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 ...
Down Syndrome Symptoms. Down syndrome is usually diagnosed during pregnancy through genetic screening or at birth through diagnostic tests. There are some distinct physical features that typically ...
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.
Not all genetic disorders directly result in death; however, there are no known cures for genetic disorders. Many genetic disorders affect stages of development, such as Down syndrome, while others result in purely physical symptoms such as muscular dystrophy. Other disorders, such as Huntington's disease, show no signs until adulthood.
This is a list of major and frequently observed neurological disorders (e.g., Alzheimer's disease), symptoms (e.g., back pain), signs (e.g., aphasia) and syndromes (e.g., Aicardi syndrome). There is disagreement over the definitions and criteria used to delineate various disorders and whether some of these conditions should be classified as ...
An anaphase lag of a chromosome 21 in a Down syndrome embryo leads to a fraction of euploid cells (2n cells), phenomenon described as "aneuploidy rescue". There is considerable variability in the fraction of cells with trisomy 21, both as a whole and tissue-by-tissue. This is the cause of 1–2% of the observed Down syndromes. [4]
A syndrome is a set of medical signs and symptoms which are correlated with each other and often associated with a particular disease or disorder. [1] The word derives from the Greek σύνδρομον, meaning "concurrence". [2]: 1818 When a syndrome is paired with a definite cause this becomes a disease. [3]