a chromosomal disorder caused by an extra copy of chromosome 21; symptoms include intellectual impairment, congenital heart ... central nervous system and metabolic disorders, and occasionally chromosomal abnormalities ... abnormalities, male genital abnormalities and short stature; caused by an abnormality in the ZEB2 gene located on chromosome 2 ... chromosomal disorder caused by mutations in the FMR1 gene on the X chromosome, resulting in an increased number of copies of a ...