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A chromosomal inversion reverses the orientation of a chromosome segment relative to its flanking sequence. Breakage and rejoining can change gene regulation at the boundaries even when the segment retains the same genes. In an individual carrying different orientations, crossing over within the inverted region can produce unbalanced products, reducing recovery of recombinant descendants. An inversion therefore affects inheritance as well as the visual order of chromosomal markers. ^[ref]

Synteny describes the occurrence of genomic loci on the same chromosome; comparative usage often additionally concerns conserved neighbourhoods or order between genomes. A block containing corresponding genes can support assignment of an uncertain region even when individual sequences have diverged. Rearrangements such as a chromosomal inversion can preserve membership of a block while reversing its internal orientation. The intended sense of conserved location versus conserved order should be stated. ^[ref]