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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.
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 ...
Rarely, a region of chromosome 21 will undergo a duplication event. This will lead to extra copies of some, but not all, of the genes on chromosome 21 (46,XX,dup(21q)). If the duplicated region has genes that are responsible for Down syndrome physical and mental characteristics, such individuals will show those characteristics.
Down syndrome neotenizes the brain and body. [56] The syndrome is characterized by decelerated maturation (neoteny), incomplete morphogenesis (vestigia) and atavisms. [56] Dwarfism and achondroplasia also neotenize the size of the human height as well as the limbs. This is due to dwarfing in the growth hormone deficiency.
Down syndrome is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. [1] It is typically associated with developmental delays, characteristic physical features, and mild to moderate intellectual disability. [2] The average IQ of a young adult with Down syndrome is 50, equivalent to the mental age of an 8 ...
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.
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.
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