Down syndrome - Symptoms and causes - Mayo Clinic
网页2018年3月8日 · Down syndrome is a genetic disorder caused when abnormal cell division results in an extra full or partial copy of chromosome 21. This extra genetic material causes the developmental changes and physical features of Down syndrome. Down syndrome varies in severity among individuals, causing lifelong intellectual disability and …
Down Syndrome: Symptoms & Causes - Cleveland Clinic
网页Down syndrome is a genetic condition where a person is born with an extra copy of chromosome 21. This means that they have a total of 47 chromosomes instead of 46. This can affect how their brain and body develop. People diagnosed with Down syndrome have happy and healthy lives with supportive care.
What causes Down syndrome? | NICHD - NICHD - Eunice …
网页2012年6月11日 · Down syndrome is caused by a random error in cell division that results in the presence of an extra copy of chromosome 21. The type of error is called nondisjunction.
Down Syndrome: Causes, Types, and Symptoms - Healthline
网页2023年11月28日 · Down syndrome is the most common genetic condition in the United States. We’ll explain the causes, symptoms, and outlook of this condition.
Down Syndrome | Birth Defects | CDC - Centers for Disease …
网页2024年5月16日 · Down syndrome is a genetic condition where a person is born with an extra chromosome. This can affect how their brain and body develop. People diagnosed with Down syndrome can lead healthy lives with supportive care.
Down syndrome - Wikipedia
网页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 chromosomes.
Down Syndrome: Causes, Symptoms, Diagnosis, and Treatment - WebMD
网页2024年2月23日 · What Causes Down Syndrome? 13 min read. What Is Down Syndrome? Down syndrome is a genetic condition that causes mild to significant physical and developmental problems. People with...
About Down Syndrome | National Down Syndrome Society (NDSS)
网页2021年4月6日 · Down syndrome is usually caused by an error in cell division called “nondisjunction.” Nondisjunction results in an embryo with three copies of chromosome 21 instead of the usual two. Prior to or at conception, a pair of 21st chromosomes in either the sperm or the egg fails to separate.
Down Syndrome - NICHD - Eunice Kennedy Shriver National …
网页2023年11月22日 · Print. Down Syndrome. Down syndrome is a set of cognitive and physical symptoms that result from having an extra chromosome 21 or an extra piece of that chromosome. It is the most common chromosomal cause of mild to moderate intellectual disabilities. People with Down syndrome are at risk for several other health conditions.
Trisomy 21 (Down Syndrome) - Children's Hospital of Philadelphia
网页Causes. Down syndrome occurs because of the extra copy of chromosome 21, which can cause the body and brain to develop differently than a child without the syndrome.