Studies on crossover-specific mutants and the distribution of crossing over in Drosophila females

Cytogenet Genome Res. 2004;107(3-4):160-71. doi: 10.1159/000080594.


In Drosophila females, the majority of recombination events do not become crossovers and those that do occur are nonrandomly distributed. Furthermore, a group of Drosophila mutants specifically reduce crossing over, suggesting that crossovers depend on different gene products than noncrossovers. In mei-218 mutants, crossing over is reduced by approximately 90% while noncrossovers and the initiation of recombination remain unchanged. Importantly, the residual crossovers have a more random distribution than wild-type. It has been proposed that mei-218 has a role in establishing the crossover distribution by determining which recombination sites become crossovers. Surprisingly, a diverse group of genes, including those required for double strand break (DSB) formation or repair, have an effect on crossover distribution. Not all of these mutants, however, have a crossover-specific defect like mei-218 and it is not understood why some crossover-defective mutants alter the distribution of crossovers. Intragenic recombination experiments suggest that mei-218 is required for a molecular transition of the recombination intermediate late in the DSB repair pathway. We propose that the changes in crossover distribution in some crossover-defective mutants are a secondary consequence of the crossover reductions. This may be the activation of a regulatory system that ensures at least one crossover per chromosome, and which compensates for an absence of crossovers by attempting to generate them at random locations.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alleles
  • Animals
  • Cell Cycle Proteins / genetics*
  • Cell Cycle Proteins / metabolism*
  • Crossing Over, Genetic / genetics*
  • Crossing Over, Genetic / radiation effects
  • DNA Damage / genetics
  • DNA Repair / genetics
  • Drosophila Proteins / genetics*
  • Drosophila Proteins / metabolism*
  • Drosophila melanogaster / genetics*
  • Drosophila melanogaster / metabolism
  • Drosophila melanogaster / radiation effects
  • Female
  • Genotype
  • Male
  • Meiosis / genetics
  • Mutation / genetics*
  • Synaptonemal Complex / metabolism
  • X-Rays


  • Cell Cycle Proteins
  • Drosophila Proteins
  • mei-218 protein, Drosophila