Definition - What does Translocations mean?
Translocations are rearrangements of chromosomes. This occurs when cells are dividing and genetic material is copied. During this process, parts of the chromosome can break off and rejoin in a different place. Translocations may occur spontaneously or be inherited from a person's parents. They can lead to developmental abnormalities in the fetus or miscarriage. Most carriers of translocations are healthy individuals who only discover their status when they are trying to conceive.
FertilitySmarts explains Translocations
Translocations can occur spontaneously at the time of conception when an error occurs in the making of the egg or sperm. They can also be inherited when a carrier of a translocation passes it down to their children. Approximately 1 in 500 people have a translocation.
There are two types of translocations, reciprocal and Robertsonian. Reciprocal translocation occurs when parts of two different chromosomes break off and swap places. In Robertsonian translocation, two entire chromosomes attach to each other to become one long chromosome. This can lead to developmental conditions, such as Translocation Down syndrome, trisomy 13, or uniparental disomy (UPD).
Translocations are also described by the amount of genetic material that remains. These are referred to as balanced or unbalanced translocations. Balanced translocations occur when chromosomes are rearranged but there is no loss or gain of chromosome material. A person with a balanced translocation does not have any health problems because of it and is simply a carrier of the translocation. In contrast, unbalanced translocations result from a missing and/or extra piece of chromosome. Unbalanced translocations can occur when a person with a balanced translocation conceives. This type of translocation can result in health problems in the baby or miscarriage.
Testing for translocations is available. This involves collecting some tissue for chromosome analysis or karyotyping. In adults, this tissue is collected using a simple blood test to determine whether or not they are carriers of translocations. In order to obtain tissue from a fetus for karyotyping, an amniocentesis or chorionic villus sampling is performed.