 Down syndrome is a genetic condition caused by an extra copy of chromosome 21. It is characterized by physical and intellectual impairments, such as delayed development, distinct facial features, and heart defects. Symptoms may include mild to moderate intellectual disability, speech delays, and physical characteristics like small stature, upward slanting eyes, and a single deep crease across the palm of the hand. Additionally, infants with Down syndrome are prone to certain medical conditions, including congenital heart defects, thyroid problems, and leukemia.