Causes of Down Syndrome

There are 3 causes of Down Syndrome.  These causes are: Trisomy 21, Mosaic Down Syndrome, and Translocation Down Syndrome.  About 95% of the time, Down Syndrome is caused by Trisomy 21.  The Child has 3 copies of chromosome 21 instead of the 2 copies in all cells.  In Mosaic Down Syndrome, children have some cells with an extra copy of chromosome 21.  This mosaic of normal and abnormal cells are caused by abnormal cell division after fertilization.  Translocation down syndrome cane occur when part of chromosome 21 becomes attached (translocated) onto another chromosome, before or at exception.  These children have the usual copy of chromosome 21, but they also have additional material from chromosome 21 attached to the translocated chromosome.  I have a friend who has Down Syndrome.  I learned that there are 3 types of Down syndrome.  What do you know about Down syndrome that you can share with me?  For more information, you can visit www.mayoclinic.org/down syndrome