pericentrici

Pericentric inversions, sometimes referred to by the plural form pericentrici, are chromosomal inversions in which the centromere lies within the inverted segment. They are distinguished from paracentric inversions, where the centromere lies outside the inverted region.

These inversions arise when two breaks occur on both sides of the centromere, followed by rejoining in the opposite orientation. In a homozygous individual, the inverted chromosome usually has no obvious phenotype. In heterozygotes, however, homologous chromosomes pair through an inverted loop during meiosis. Crossing over within this loop can generate recombinant chromatids that are acentric or dicentric, leading to duplications and deletions in the gametes and often producing inviable or subfertile offspring. As a result, recombination is suppressed within the inverted segment, effectively locking together the genes inside the inversion.

Pericentric inversions alter the linear order of genes on the affected chromosome and can change genetic map distances. They can maintain linkage among coadapted alleles, contributing to local adaptation or the preservation of complex trait combinations. Over evolutionary time, repeated inversions can affect chromosome structure and may influence speciation by reducing gene flow in inverted regions.

Detection and study of pericentric inversions rely on cytogenetic techniques such as chromosome banding and fluorescence in situ hybridization, as well as modern sequencing to confirm breakpoints and the inverted gene order. In humans and other species, pericentric inversions are among the best-characterized chromosomal rearrangements and remain an important subject in medical genetics and evolutionary genomics.

See also: paracentric inversion, chromosome inversion, karyotype analysis.