1.+What+Causes+It?



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 * Down Syndrome or Trisonomy 21 is caused by an extra 21st chromosome which happens during cell division. During fetilization between a sperm and an egg, the child recieves 23 sets of chromosomes from the father and 23 from the mother for a total of 46 chromosomes. However, people with DS have a total set of 47 chromosomes. This is called a nondisjunction since there was a problem with the chromosomes seperating properly.
 * Nondisjunction simply means that there are more or fewer chromosomes than normal. But in this case, there is one more chromosome than normal.
 * It's true that older women are at a higher risk for having a child with Down Syndrome, (the chance increases as the woman gets older), but most babies with Down Syndrome are born to women under 35 years of age.