translocation
Last reviewed 01/2018
Translocation:
- a translocation involves the breakage and removal
of a large segment of DNA from one chromosome, followed by the segment's attachment
to a different chromosome
- a balanced (reciprocal) translocation is an even
swap made between two chromosomes
- if the exchange results in no loss or gain of DNA, the individual is clinically normal and is said to have a balanced translocation and is a translocation carrier. He/she is, however, at risk of having a chromosomally abnormal baby (an unbalanced translocation.)
- a Robertsonian translocation occurs when the long arms of two acrocentric chromosomes fuse at a centromere, and the two short arms are lost
- a balanced (reciprocal) translocation is an even
swap made between two chromosomes
- abnormalities resulting from an unbalanced translocation depend on the particular chromosome fragments present in monosomic or trisomic form. Sometimes spontaneous abortion is inevitable; in other cases a child with multiple abnormalities may be born alive
- risk of an unbalanced karyotype in a child depends on the individual translocation. Once a translocation has been identified it is important to investigate relatives to identify carriers of the balanced translocation so that genetic information and prenatal diagnosis can be offered