Editing Chromosomal translocation (section)

==Balanced reciprocal translocations==
Reciprocal translocations involve an ''exchange'' of material between non-homologous chromosomes.<ref name=":7">{{Citation |last1=Therman |first1=Eeva |title=Reciprocal Translocations |date=1993 |work=Human Chromosomes: Structure, Behavior, and Effects |pages=273–287 |editor-last=Therman |editor-first=Eeva |url=https://link.springer.com/chapter/10.1007/978-1-4684-0529-3_26 |access-date=2025-04-02 |place=New York, NY |publisher=Springer US |language=en |doi=10.1007/978-1-4684-0529-3_26 |isbn=978-1-4684-0529-3 |last2=Susman |first2=Millard |editor2-last=Susman |editor2-first=Millard|url-access=subscription }}</ref> Such translocations are usually harmless, as they do not result in a gain or loss of genetic material, as is the case with nonreciprocal translocations. This type of translocation is often caused by erroneous repair of double stranded breaks or non-homologous crossing over in meiosis.<ref name=":7" />

A common balanced reciprocal translocation is the exchange of material between chromosome 11 and 22. Individuals with this chromosomal abnormality do not experience any phenotypic effects but are subject to issues with fertility since carriers of balanced reciprocal translocations may create [[gamete]]s with ''unbalanced'' reciprocal or nonreciprocal chromosome translocations.<ref name=":8">{{Citation |last1=Wilch |first1=Ellen S. |title=Historical and Clinical Perspectives on Chromosomal Translocations |date=2018 |work=Chromosome Translocation |pages=1–14 |editor-last=Zhang |editor-first=Yu |url=https://link.springer.com/chapter/10.1007/978-981-13-0593-1_1 |access-date=2025-04-02 |place=Singapore |publisher=Springer |language=en |doi=10.1007/978-981-13-0593-1_1 |isbn=978-981-13-0593-1 |last2=Morton |first2=Cynthia C.|volume=1044 |pmid=29956287 |url-access=subscription }}</ref> The combination of the carrier’s gamete with the wild type gamete from the other parent may result in duplication or deletion of genetic material based on segregation of chromosomes during meiosis.<ref name=":8" /> This can lead to infertility, [[miscarriage]]s or [[children]] with abnormalities. [[Genetic counseling|Genetic counselling]] and [[genetic testing]] are often offered to families that may carry a translocation. A common example of a birth defect that may result from the carrier of the translocation mentioned above is Emanuel Syndrome.<ref name=":9">{{Cite web |last=PMC |first=Europe |title=Europe PMC |url=https://europepmc.org/article/NBK/nbk1263 |access-date=2025-04-02 |website=europepmc.org |language=en}}</ref>

{{Heading|Unbalanced reciprocal translocations}}

Unbalanced reciprocal translocations are similar to balanced reciprocal translocations in that they involve the ''exchange'' of genetic information between two non-homologous chromosomes.<ref name=":10">{{cite journal |last1=Parslow |first1=Malcolm |last2=Chambers |first2=Diana |last3=Aftimos |first3=Salim |title=An inherited reciprocal translocation—balanced or unbalanced? |journal=Pathology |date=1981 |volume=13 |issue=1 |pages=174 |doi=10.1016/S0031-3025(16)38470-7 }}</ref> However, with unbalanced reciprocal translocations, the process results in the duplication or deletion of some genetic material as well. Since there is a genetic imbalance, individuals with an unbalanced reciprocal translocation will often exhibit [[phenotype]] reflective of the abnormal gene expression.<ref name=":10" />

Most unbalanced reciprocal translocations are a result of inheritance from a parent with a balanced translocation.<ref name=":11">{{cite journal |last1=Chen |first1=Chih-Ping |last2=Wu |first2=Pei-Chen |last3=Lin |first3=Chen-Ju |last4=Chern |first4=Schu-Rern |last5=Tsai |first5=Fuu-Jen |last6=Lee |first6=Chen-Chi |last7=Town |first7=Dai-Dyi |last8=Chen |first8=Wen-Lin |last9=Chen |first9=Li-Feng |last10=Lee |first10=Meng-Shan |last11=Pan |first11=Chen-Wen |last12=Wang |first12=Wayseen |title=Unbalanced reciprocal translocations at amniocentesis |journal=Taiwanese Journal of Obstetrics and Gynecology |date=March 2011 |volume=50 |issue=1 |pages=48–57 |doi=10.1016/j.tjog.2011.02.001 |pmid=21482375 |doi-access=free }}</ref> As mentioned previously, parents with balanced translocations are likely to give birth to children with unbalanced translocations. Although less common, unbalanced translocations may form due to errors during [[gametogenesis]] or errors in repair of double stranded DNA breaks.<ref name=":11" />