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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 ...
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.
[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 ...
The fluid is then tested for chromosomal abnormalities such as Down syndrome (trisomy 21) and trisomy 18, which can result in neonatal or fetal death. Test results can be retrieved within 7–14 days after the test is done. This method is 99.4% accurate at detecting and diagnosing fetal chromosome abnormalities.
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 ...
[8] 45% of children with Down syndrome have congenital heart disease. Of these, 35–40% have AV septal defects. [ 9 ] Approximately 40-50% of fetuses diagnosed with AVCD have Down syndrome, and a further 15-20% are associated with other chromosomal abnormalities and syndromes, such as DiGeorge syndrome .
Cat eye syndrome; Caudal regression syndrome; Sotos syndrome Cerebral Gigantism; CHARGE syndrome; Chromosome 16 abnormalities; Chromosome 18 abnormalities; Chromosome 20 abnormalities; Chromosome 22 abnormalities; Cleft lip/palate; Cleidocranial dysostosis; Club foot; Congenital adrenal hyperplasia (CAH) Congenital central hypoventilation syndrome