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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 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.
Down Syndrome Risk Factors Advanced maternal age is thought to be the greatest risk factor for Down syndrome, as a mother's eggs, when older, have more chance of chromosomal abnormalities.
Atypical motor development such as persistent primitive reflexes beyond 4–6 months, or delayed walking may be an indication of developmental delays or conditions such as autism, cerebral palsy, or down syndrome. [53] Lower motor coordination results in difficulties with speed accuracy and with trade-off in complex tasks.
The scientific study of the causes of developmental disorders involves many theories. Some of the major differences between these theories involves whether environment disrupts normal development, if abnormalities are pre-determined, or if they are products of human evolutionary history which become disorders in modern environments (see evolutionary psychiatry). [5]
Global developmental delay is an umbrella term used when children are significantly delayed in two or more areas of development. It can be diagnosed when a child is delayed in one or more milestones, categorised into motor skills, speech, cognitive skills, and social and emotional development. [1]
March 21 (3/21) is World Down Syndrome Day, chosen because people with Down Syndrome have three copies of the 21st chromosome instead of the usual two. "Gabe lives his life to the fullest," Nick ...
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]