A translocation is formed when there has been transfer of material between chromosomes, requiring breakage of both chromosomes, with repair in an abnormal arrangement.

If the exchange results in no loss or gain of DNA, the individual is clinically normal and is said to have a balanced translocation.

Such a balanced translocation carrier is, however, at risk of producing chromosomally unbalanced gametes.

Some translocations occur de novo, but most are inherited from a parent. It is therefore important to investigate relatives so that genetic advice and prenatal diagnosis can be offered.