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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.
Trisomy 21 is the cause of approximately 95% of observed Down syndrome, with 88% coming from nondisjunction in the maternal gamete and 8% coming from nondisjunction in the paternal gamete. [4] Mitotic nondisjunction after conception would lead to mosaicism, and is discussed later. Some cases have been reported of people with Down syndrome ...
[1] [2] Understanding the genes involved may help to target medical treatment to individuals with Down syndrome. It is estimated that chromosome 21 contains 200 to 250 genes. [3] Recent research has identified a region of the chromosome that contains the main genes responsible for the pathogenesis of Down syndrome, [4] located proximal to 21q22 ...
When there is an extra chromosome 21, the result is Down syndrome. There are three genetic variations of Down syndrome: Trisomy 21: This occurs when there is a third copy of chromosome 21. This is ...
Down syndrome (trisomy 21) is characterized by features of accelerated aging including premature greying of hair and deficient DNA repair. [3] Premature greying needs to be differentiated from various genetic hypomelanotic hair disorders. Smoking is another factor that is considered to be related to premature greying of hair.
Trisomy 21, one of the three types of Down syndrome, indicates that an individual has a duplicate of chromosome 21. The extra chromosome changes how one’s brain and body develop, and can lead to ...
Rather than having monosomy, or only one copy, the majority of aneuploid people have trisomy, or three copies of one chromosome. [citation needed] An example of trisomy in humans is Down syndrome, which is a developmental disorder caused by an extra copy of chromosome 21; the disorder is therefore also called trisomy 21. [7]
DSCAM and Dscam are both abbreviations for Down syndrome cell adhesion molecule. [5] In humans, DSCAM refers to a gene that encodes one of several protein isoforms. [6] Down syndrome (DS), caused by trisomy 21, is the most common birth defect associated with intellectual disability. DSCAM plays a crucial role in the development of DS: it is ...