what is down syndrome

Down syndrome is a genetic condition that occurs when an individual has an extra copy of chromosome 21. Typically, a baby is born with 46 chromosomes, but babies with Down syndrome have an extra copy of one of these chromosomes, which is why Down syndrome is also referred to as Trisomy 21. This extra copy changes how the baby’s body and brain develop, which can cause both mental and physical challenges for the baby. Some common physical traits of Down syndrome include low muscle tone, small stature, an upward slant to the eyes, and a single deep crease across the center of the palm. People with Down syndrome usually have an IQ (a measure of intelligence) in the mildly-to-moderately low range and are slower to speak than other children. Down syndrome varies in severity among individuals, causing lifelong intellectual disability and developmental delays. It is the most common genetic chromosomal disorder and cause of learning disabilities in children. Down syndrome is usually not inherited and happens by chance, as an error when cells are dividing during early development.