The document discusses several chromosomal abnormalities that can cause intellectual disability, including Down syndrome, Fragile X syndrome, Trisomy 18, and Trisomy 13. Down syndrome results from a trisomy of chromosome 21 and is the most common chromosomal cause of intellectual disability. It can cause distinctive facial features and health issues. Fragile X syndrome is an inherited condition linked to the X chromosome and is characterized by developmental delays and autism-like features. Trisomy 18 and 13 involve an extra chromosome 18 or 13, respectively, and often result in growth problems and death in infancy.