Inversion

Definition

A chromosomal rearrangement in which a segment of DNA is reversed end-to-end, or a developmental process in which an embryo or structure turns inside-out. In genetics, inversions suppress recombination within the inverted region and may create balanced polymorphisms that maintain adaptive gene complexes. In embryology, inversion describes the eversion of germ layers or the turning of an embryo during development.

Etymology

From Latin inversio, from invertere 'to turn upside down, invert'

Example

The 'In(2L)t' inversion on the left arm of chromosome 2 in Drosophila melanogaster is a classic polymorphism maintained by climatic selection; heterokaryotypes carrying alternate arrangements show suppressed recombination and carry distinct suites of thermal-adaptation alleles.

Related Terms

• chromosomal rearrangement
• Translocation
• paracentric inversion
• pericentric inversion
• heterokaryotype
• recombination suppression
• inversion clade

Usage Notes

Distinguish between paracentric inversions (not involving the centromere) and pericentric inversions (including the centromere). In population genetics, 'inversion' often refers to the polymorphic arrangement rather than the mutational event. In developmental contexts (e.g., some mollusk and ascidian embryos), 'inversion' describes morphogenetic movements unrelated to chromosomal structure.