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.
In this type of chromosomal change, only part of an extra copy of chromosome 21 is in the cells. The extra part of the chromosome gets stuck to another chromosome and gets transmitted into other cells as the cells divide. This type of change causes about 4% of Down syndrome cases.