Chromosomal inversion
（重定向自Pericentric inversion）
![A clay model showing why heterozygous inversion loops are visible in polytene chromosome preparations](/Images/godic/202502/02/Inversioncartoon1800.gif")
![An inversion loop in the A arm of a chromosome from an Axarus species midge](/Images/godic/202502/02/A_arm_inversion1800.jpg")
An inversion is a chromosome rearrangement in which a segment of a chromosome is reversed end to end. An inversion occurs when a single chromosome undergoes breakage and rearrangement within itself. Inversions are of two types: paracentric and pericentric.