Reciprocal translocation is a chromosome abnormality caused by exchange of parts between non-homologous chromosomes. Two detached fragments of two different chromosomes are switched.
In genetics, chromosome translocation is a phenomenon that results in unusual rearrangement of chromosomes. This includes balanced and unbalanced translocation, with two main types: reciprocal-, and Robertsonian translocation. Reciprocal translocation is a chromosome abnormality caused by exchange of parts between non-homologous chromosomes. Two detached fragments of two different chromosomes are switched. Robertsonian translocation occurs when two non-homologous chromosomes get attached, meaning that given two healthy pairs of chromosomes, one of each pair “sticks“ together.
A gene fusion may be created when the translocation joins two otherwise-separated genes. It is detected on cytogenetics or a karyotype of affected cells. Translocations can be balanced (in an even exchange of material with no genetic information extra or missing, and ideally full functionality) or unbalanced (where the exchange of chromosome material is unequal resulting in extra or missing genes).
Reciprocal translocations are usually an exchange of material between non-homologous chromosomes. Estimates of incidence range from about 1 in 500 to 1 in 625 human newborns. Such translocations are usually harmless and may be found through prenatal diagnosis. However, carriers of balanced reciprocal translocations have increased risks of creating gametes with unbalanced chromosome translocations, leading to Infertility, miscarriages or children with abnormalities. Genetic counseling and genetic testing are often offered to families that may carry a translocation. Most balanced translocation carriers are healthy and do not have any symptoms.
It is important to distinguish between chromosomal translocations occurring in gametogenesis, due to errors in meiosis, and translocations that occur in cellular division of somatic cells, due to errors in mitosis. The former results in a chromosomal abnormality featured in all cells of the offspring, as in translocation carriers. Somatic translocations, on the other hand, result in abnormalities featured only in the affected cell line, as in chronic myelogenous leukemia with the Philadelphia chromosome translocation.
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