Iran received $4.2 billion in similar payments under the 2013 interim agreement with the United States and was then given another $2.8 billion by the Obama administration last year in a bid to keep Iran committed to the talks through November, when negotiators parted ways without reaching an agreement.
The DNA in our chromosomes determines how we develop. Down syndrome is caused when there is an extra chromosome. People with Down syndrome have 47 chromosomes in their cells instead of 46. They have an extra chromosome 21, which is why Down syndrome is also sometimes known as trisomy 21. Although we know how Down syndrome occurs, we do not yet know why it happens.
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. Any one of three genetic variations can cause Down syndrome: 1  Trisomy 21.2  About 95 percent of the time, Down syndrome is caused by trisomy 21 â the child has three copies of chromosome 21 (instead of the usual two copies) in all cells. Mosaic Down syndrome. 2  In this rare form of Down syndrome, children have some cells with an extra copy of chromosome 21. 3  This mosaic of normal and abnormal cells is caused by abnormal cell division after fertilization. 4  Translocation Down syndrome.