What Is a Translocation?

There are two types of translocations –– reciprocal and Robertsonian

Chromosomes, artwork. Credit: Science Photo Library - SCIEPRO / Getty Images

Our bodies are made up of a variety of parts that work together so that we can go about our day to day functions. Within our bodies are cells, and within those cells are chromosomes, which contain DNA –– our bodies genetic instructions. Most people have 23 chromosome pairs, 46 chromosomes in total. Sometimes there are errors in our chromosomes, which can mess up the genetic code, or blueprint, for our body.

One of these chromosomal errors is known as a translocation. Translocations occur when a piece of a chromosome breaks off and sticks to another chromosome. When this happens the result can range from barely noticable to the miscarriage of a fetus. There are two types of chromosome translocations –– reciprocal translocations and Robertsonian translocations. 

Reciprocal Translocations

A reciprocal translocation, also known as a balanced translocation, occurs when pieces of two different chromosomes change places. People who have reciprocal translocations are known as carriers. They carry this type of chromosomal abnormality but have little to no health problems themselves. Most people with balanced translocations do not have any health issues or developmental delays. However, they may have issues when trying to conceive. 

Most people with reciprocal translocations have no idea they have the condition until they have difficulty getting pregnant or have a child with a chromosomal abnormality.

If your doctor suspects you have a translocation, they may order a karyotype, which can be done through a blood test. During pregnancy, if a karyotype determines your child has a balanced translocation, your doctor may want to screen you as well to determine if the translocation was inherited. If your child inherits the translocation, chances are they won't have any developmental or health problems either.

 

Reciprocal translocations happen naturally. There is nothing you can or could have done to prevent it. If you have a balanced translocation and are concerned about passing down any chromosomal abnormalities, a genetic counselor can help you better understand your risks. 

Robertsonian Translocation

A Robertsonian translocation, named after the doctor who discovered this type of translocation in grasshopers, occurs when one whole chromosome attaches to another chromosome. One in 1,000 babies is born with this type of translocation. Some people can be Robertsonian translocation carriers, and have no symptoms. People who are carriers are more likely to suffer from recurrent miscarriages. Other people might have severe health problems and developmental delays. 

Some cases of Down syndrome are caused by Robertsonian translocations involving chromosome 21. Robertsonian translocations on chromosome 13 may cause Patau syndrome –– an almost always fatal genetic condition that can lead to miscarriage or early death (usually before the age of one).

Robertsonian translocations related to chromosome 14 can cause developmental delays. And translocations on chromosome 15 can cause features of Prader-Willi syndrome or Angelman syndrome. Down syndrome is the most common Robertsonian translocation. 

If you are a carrier of a Robertsonian translocation, a genetic counselor can help you understand your risks of passing on the translocation or having a child with a non-carrier type of Robertsonian translocation. 

Source:

RareChromo. Balanced Translocations. (2014).

RareChromo. Robertsonian Translocations. (2005)

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