Ok. this is an easy one. I'm glad you asked that question.
XX or XY is a chormosome that identifies whether we are male or female.
Down syndrome is the case of an extra chromosome because we all have 46 chromosomes, which means they're a rod shaped portions of DNA organized in 23 pairs. Each parent of a child provides one of the two chromosomes in each of the 23 pairs of chromosomes. At conception, 23 maternal and 23 paternal chromosomes unite within a signle cell called the zygote. These 46 chromosomes in the zygote contain the genetic blueprint that will guide cell activity for the rest of the child's life. What this means is....both parents each provide 23 chormosomes when a child is conceived that unite and form a single cell called the zygote. This zygote is the make up of who they are. Their genes are in this.
what you're asking about chromosome abnormalties...Down Syndrome is one form of a chromosome abnormalty, thus, having an extra chromosome in the 21st pair Down Syndrome, or Downs, is the most frequent cause of mental retardation. This usually occurs when the mother is unusually young or old during pregnancy.
Fragile X syndrome is a disorder produced by injury to a gene on the X chromosome, which produces mild to moderate mental retardation.
This next syndrome is a little more complicated to pronounce, but it's Klinefelter's syndrome, which is a disorder resulting from the presence of an extra X chromosome that producses underdeveloped genitals, extreme height, and enlarged breasts. THIS is the syndrome you're looking for. THIS is the syndrome those who have genital disorders, hence, giving the individual confusing looking genitals that make them either male or female. Sometimes this is can be corrected with surgery. This syndrome is quite common...more common than we think, and it's only now that it's come to our attention, that people do suffer from this syndrome. It's not a disease, it's just a condition that the sufferers live with, and they dont die from it.