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
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
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