An inversion is a type of chromosomal structural variation where a segment of a chromosome is reversed end to end. This means that a section of the chromosome is cut out, flipped, and reinserted in the opposite orientation. Inversions can disrupt gene function and regulation, leading to various genetic consequences.

Types of Inversions

Inversions are classified based on whether they include the centromere (See in above figure).

1. Pericentric Inversion: Pericentric Inversion is defined as a type of inversion that includes the centromere.

   • Consequences: Can involve the flipping of large segments of the chromosome, affecting the relative positions of genes on either side of the centromere. During meiosis, pericentric inversions can lead to the production of gametes with duplications and deletions of chromosomal segments, increasing the risk of genetic disorders in offspring.

2. Paracentric Inversion: Paracentric Inversion is another type of inversion wherein the centromere is not involved in inversion and occurs entirely within one arm of the chromosome.

   • Consequences: Paracentric inversions can disrupt gene sequences and regulatory regions within the chromosome arm. During meiosis, they can lead to the formation of dicentric (two centromeres) or acentric (no centromere) chromosomes in the gametes, which are often non-viable.