The gene for FA codes for a protein called frataxin.
Normal frataxin is found in the cellular energy structures known as mitochondria, where it is thought to be involved in regulating the transport of iron.
In FA, the frataxin gene on chromosome 9 is expanded when a particular sequence of bases in the DNA is repeated too many times.
Ordinarily, there are seven to 22 repeats of the frataxin gene; in FA, this sequence may be repeated between 800 to 1,000 times.
This extra DNA interferes with normal production of frataxin, thereby impairing iron transport.