Which condition is characterized by intellectual disability and physical disorders due to an extra copy of chromosome 21?

Down syndrome is characterized by the presence of an extra copy of chromosome 21, a condition known as trisomy 21. This genetic anomaly leads to intellectual disability along with various physical disorders, which can include features such as a flat facial profile, slanted eyes, and a short neck, among other potential health issues. Individuals with Down syndrome often experience developmental delays and may have congenital heart defects or gastrointestinal problems.

The correct identification of Down syndrome as the condition linked to this specific chromosomal abnormality sets it apart from the other options. For instance, Fragile X syndrome is a genetic condition caused by a mutation in the FMR1 gene and is the most common inherited cause of intellectual disability. Cystic fibrosis is a hereditary disorder affecting the lungs and digestive system due to mutations in the CFTR gene. Hemophilia is primarily a group of hereditary bleeding disorders caused by a deficiency of certain clotting factors in the blood. Each of these conditions involves different genetic causes and health implications, making Down syndrome uniquely defined by the presence of an extra chromosome 21.