chromosomal rearrangement in which a segment of genetic material is broken
away from the chromosome, inverted from end to end, and re-inserted into
the chromosome at the same breakage site. Balanced inversions (no net loss
or gain of genetic material) are usually not associated with phenotypic abnormalities,
although in some cases gene disruptions at the breakpoints can cause adverse
phenotypic effects, including some known genetic diseases; unbalanced inversions
(loss or gain of chromosome material) nearly always yield an abnormal phenotype.
Definition from: GeneReviews
from the University of Washington and the National Center for Biotechnology Information
Related discussion in the Handbook
See also Understanding Medical Terminology.