The joy of balancers

PLoS Genet. 2019 Nov 7;15(11):e1008421. doi: 10.1371/journal.pgen.1008421. eCollection 2019 Nov.


Balancer chromosomes are multiply inverted and rearranged chromosomes that are widely used in Drosophila genetics. First described nearly 100 years ago, balancers are used extensively in stock maintenance and complex crosses. Recently, the complete molecular structures of several commonly used balancers were determined by whole-genome sequencing. This revealed a surprising amount of variation among balancers derived from a common progenitor, identified genes directly affected by inversion breakpoints, and cataloged mutations shared by balancers. These studies emphasized that it is important to choose the optimal balancer, because different inversions suppress meiotic recombination in different chromosomal regions. In this review, we provide a brief history of balancers in Drosophila, discuss how they are used today, and provide examples of unexpected recombination events involving balancers that can lead to stock breakdown.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Animals
  • Centromere / genetics
  • Chromosome Inversion / genetics*
  • Chromosomes, Insect / genetics*
  • Drosophila melanogaster / genetics
  • Genome, Insect / genetics
  • Heterochromatin / genetics*
  • Homologous Recombination / genetics*
  • Phenotype
  • Sequence Deletion / genetics
  • X Chromosome / genetics


  • Heterochromatin