Down syndrome symptoms: People with Down syndrome have an

People with Down syndrome have an extra chromosome that impacts their looks and their ability to think, learn, and reason. Discover the type, causes, and kinds of effects it can have. Down syndrome is a genetic condition where a person has an extra copy of chromosome 21. It can affect their physical, cognitive and behavioral development. Learn about the types, risk factors, screening and diagnostic tests for Down syndrome . About 1 in 700 babies are born with the birth defect known as Down Syndrome . Learn about the different Down Syndrome types and related health issues. Down syndrome is caused by an extra chromosome 21, affecting physical and intellectual development. Common physical traits of Down syndrome include a round face, upturned eyes, and a short build. Down syndrome increases the risk of developing complications and other health conditions.