Chromosomal Aberrations

An inversion is the rotation of a broken chromosome segment in such a way that it rejoins the chromosome in a reversed state, or is flipped, end to end. Inversions are usually characterized by whether the centromere is included in the inverted segment. Inversions containing the centromere are called pericentric. Those not containing the centromere are called paracentric. Although an inversion does not change the overall content of cellular DNA and can be considered a balanced translocation, it can affect a gene at many levels because it alters the normal DNA sequence. The gene may not produce its corresponding protein at all, or a nonfunctioning protein may result. There is a common inversion seen in human chromosomes involving chromosome 9. A small pericentric inversion is present in approximately 1 percent of tested individuals. There appears to be no detrimental effect on the carrier, and it does not appear to cause miscarriage or unbalanced off-spring.