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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 ...
Genetics of Down syndrome. Down syndrome is a chromosomal abnormality characterized by the presence of an extra copy of genetic material on chromosome 21, either in whole (trisomy 21) or part (such as due to translocations). The effects of the extra copy varies greatly from individual to individual, depending on the extent of the extra copy ...
Down syndrome is a genetic disorder that often results in distinct physical differences and intellectual disability. According to the Centers for Disease Control, each year about 6,000 babies are ...
Dup - Duplication of a gene or genes. C – Whole chromosome extra, missing, or both (see chromosome abnormality) T – Trinucleotide repeat disorders: gene is extended in length. A cherry red spot, which can be a feature of several storage disorders, including Tay–Sachs disease. Disorder. Chromosome. Mutation.
She and Doyle had genetic testing done, and were told that the fetus had tested positive for trisomy 21, a type of Down syndrome, a condition in which individuals have an extra copy of a chromosome.
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 ...
John Langdon Down. John Langdon Haydon Down (18 November 1828 – 7 October 1896) was a British physician best known for his description of the genetic condition now known as Down syndrome, which he originally classified in 1862. He is also noted for his work in social medicine and as a pioneer in the care of mentally disabled patients.
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