XIST

While treatment for genetic disorders seems improbable, as the therapy would have to affect each cell in the patient's body, there has been promising development in this field, as scientists have found a gene that could potentially remove, that is silence, extra chromosomes that arise in genetic disorders such as Down's Syndrome. 

This gene is called XIST, short for X-inactive specific transcript, and it is found on the X chromosomes of all female placental mammals. Because females have two X chromosomes, while males have only one, the greater amount of material produced by the two X chromosomes could be dangerous, so one of the X chromosomes is silenced, that is the chromosome is coated in heterochromatin, a substance which is created by the XIST gene, and does not allow most of the chromosome to undergo gene expression. 

Scientist are looking into using the gene to silence other chromosomes. The gene could potentially be used to treat patients with disorders with extra chromosomes. Researchers have successfully silenced an extra chromosome 21 in an artificially grown Down's syndrome cell.

There is much work to be done before this treatment can actually be used to help people, and there is much debate on whether it would work, because there is a chance that the gene would silence other chromosomes instead of the one that was targeted.

http://phenomena.nationalgeographic.com/2013/07/17/how-to-shut-down-the-extra-chromosome-in-downs-syndrome/