A reciprocal translocation is a chromosome abnormality in which two chromosomes from different couples swap parts of their genetic material. A 13th chromosome, for example, could exchange genetic material with a 16th chromosome. Reciprocal translocations do not always result in health problems, but they can reduce fertility. Certain types of translocations have been linked to health problems, such as an increased risk of mantle cell lymphoma in people who have a reciprocal translocation between the 14th and 11th chromosomes.
This happens during meiosis, the process in which chromosomes combine genetic material to create a set of diverse daughter cells, ensuring that offspring inherit a diverse set of traits. Chromosomes only swap genetic material with chromosomes in the same pair in a healthy meiosis. Material jumps between chromosomes in separate pairs in a reciprocal translocation, resulting in derivative chromosomes. The daughter cell may be able to successfully fuse with another daughter cell to create a zygote that becomes a carrier of the translocation, or the cell may be useless for reproduction, rendering it infertile, depending on the material swapped.
The same amount of material is swapped between chromosomes in a balanced reciprocal translocation. Unbalanced translocations involve chromosome segments of varying lengths. These are more likely to cause infertility and health issues; if one chromosome in a pair is shortened and the other contains a deleterious gene, the gene may express because a healthy section of chromosome to override it is missing.
Congenital disorders have been linked to reciprocal translocations, particularly in cases where people with translocations reproduce and pass on defective chromosomes to their offspring. Others may go unnoticed, and in some cases, they may even be beneficial to evolution. For a wide range of species, the ability to exchange and shuffle genetic material during sexual reproduction has proven beneficial, and translocations may occasionally provide an advantage.
When one or more chromosomes appear abnormal or there is a sequence on a chromosome that clearly does not belong, signs of a reciprocal translocation can be discovered during genetic testing. Fertility specialists can help people with translocations who are having difficulty conceiving. It may be possible to fertilize an egg using assisted reproduction, or other options such as donor eggs or sperm may be required to achieve a healthy pregnancy.