Down syndrome - Wikipedia
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 …
Down syndrome - Symptoms and causes - Mayo Clinic
Nov 12, 2024 · Down syndrome is a genetic condition caused when an unusual cell division results in an extra full or partial copy of chromosome 21. This extra genetic material causes the developmental …
Trisomy 21 (Down Syndrome) | Children's Hospital of Philadelphia
What is Trisomy 21 (Down syndrome)? Trisomy 21 is the most common chromosomal anomaly in humans, affecting about 5,000 babies born each year and more than 350,000 people in the United …
Down Syndrome | Birth Defects | CDC
Dec 26, 2024 · Down syndrome is a condition in which a person has an extra copy of chromosome 21. Chromosomes are small "packages" of genes in the body's cells, which determine how the body …
Down syndrome - PMC
Down syndrome (DS) is the most common genomic disorder of intellectual disability and is caused by trisomy of Homo sapiens chromosome 21 (HSA21). The eponym of the syndrome is from Down, who …
Down syndrome - Harvard Health
Jun 25, 2025 · Down syndrome is a disorder caused by having an extra chromosome. Chromosomes are pieces of DNA that have the blueprint for the human body. Normally a person has two copies of …
Down Syndrome (Trisomy 21) in Children
Down syndrome is a genetic disorder. It is also called trisomy 21. It includes certain birth defects, learning problems, and facial features. A child with Down syndrome also may have heart defects and …
Down Syndrome (Trisomy 21) - Children's Health Issues - MSD …
Down Syndrome (Trisomy 21) - Learn about the causes, symptoms, diagnosis & treatment from the MSD Manuals - Medical Consumer Version.
About Down Syndrome - National Human Genome Research Institute
Jun 29, 2017 · Trisomy 21 means that each cell in the body has three copies of chromosome 21 instead of the usual two copies. Having an extra number 21 chromosome interrupts the normal course of …
Trisomy 21: What you need to know - Massachusetts General Hospital
Trisomy 21 (more commonly known as Down syndrome) is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. Learn how it happens.