Science Behind DOWN syndrome.
Have you ever wondered why there are people like them? or ask someone why are they like that? well, Science can explain that.
According to Mayo Clinic, Down syndrome results when abnormal cell division involving chromosome 21 occurs (each cell normally contains 23 pairs of chromosomes). These cell division abnormalities result in extra genetic material from chromosome 21, which is responsible for the characteristic features and developmental problems of Down syndrome.
There are three genetic variations that can cause Down Syndrome:
The first one is Trisomy 21.
sorce: http://noahsdad.com/nordstrom/
About 95 percent of the time, Down syndrome is caused by trisomy 21 — the child has three copies of chromosome 21 (instead of the usual two copies) in all cells. This is caused by abnormal cell division during the development of the sperm cell or the egg cell.
The second genetic variation is Mosaic Down syndrome.
source: http://www.slideshare.net/twgriffin10/down-syndrome-4993709
In this rare form of Down syndrome, children have some cells with an extra copy of chromosome 21. This mosaic of normal and abnormal cells is caused by abnormal cell division after fertilization.
The last variation is Translocation Down syndrome.
source: http://www.mayoclinic.org/diseases-conditions/down-syndrome/basics/symptoms/con-20020948.
Down syndrome can also occur when part of chromosome 21 becomes attached (translocated) onto another chromosome, before or at conception. These children have the usual two copies of chromosome 21, but they also have additional material from chromosome 21 attached to the translocated chromosome.
For more information about Down syndrome, you can visit http://www.mayoclinic.org/diseases-conditions/down-syndrome/basics/symptoms/con-20020948.
