Chromosomal translocation

In genetics, chromomal translocations are the breaking and inappropriate merging of two different chromosomes. It is detected on cytogenetics or a karyogram of affected cells.

Translocations generally occur between regions of the DNA that are homologous. A number occurs during meiosis, while other occur later in a person's lifetime, leading for example to the formation of the Philadelphia chromosome (translocation from part of the 9th to the 22th chromosome and vice versa).

Other diseases caused by translocations are:

• Cancer - several forms of cancer are caused by translocations; this has been described mainly in leukemia (acute myelogenous leukemia and chronic myelogenous leukemia).
• Infertility (one of the would-be parents carries a balanced translocation, where the parent is asymptomatic but conceived fetuses are not viable).
• Down's syndrome is caused in a minority (5% or less) of cases by a Robertsonian translocation.