Down Syndrome Cell division is of vital importance to our body. The division of cells occurs in two ways, mitosis and meiosis. Cell division occurs from chromosomes, which are the holders of genes. Many errors can occur during cell division, within the chromosomes. In meiosis, the pairs of chromosomes are supposed to split up and go to different spots in the dividing cell, this is referred to as disjunction. But sometimes one pair doesn’t divide, and the whole pair goes to one spot. This means that the resulting cells, one with 24 chromosomes and the other with 22 chromosomes. This occurrence is called nondisjunction. If a sperm or egg with an abnormal number of chromosomes merges with a normal mate, the resulting fertilized egg will have an abnormal number of chromosomes. In Down syndrome, 95% of all cases are caused by this event, one cell would have two 21st chromosomes instead of one, so the resulting fertilized egg has three 21st chromosomes. This is why the scientific name is Trisomy 21. Approximately 90% of the abnormal cells are the eggs, meaning trisomy 21 occurs mostly due to the female’s genetic code. The cause of nondisjunction isn’t known, but there is a connection with maternal age. Due to this mutation or abnormality during cell division, a child is born with Down syndrome. When a child is born with Down syndrome, there are mutations in other cell developments, such as tissue development and bone development. Body parts that are affected include: eyes,