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Examination of Mitotic and Meiotic Fission Yeast Nuclear Dynamics by Fluorescence Live-cell Microscopy
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Examination of Mitotic and Meiotic Fission Yeast Nuclear Dynamics by Fluorescence Live-cell Microscopy

Published on: June 24, 2019

Crossing over is rarely associated with mitotic intragenic recombination in Schizosaccharomyces pombe

J B Virgin1, J P Bailey, F Hasteh

  • 1Department of Pathology, Wayne State University, Detroit, Michigan, USA. jvirgin@u.washington.edu

Genetics
|January 5, 2001
PubMed

Insights

Mitotic ectopic recombination in fission yeast is infrequent and rarely involves crossing over. Diploid-specific factors appear to inhibit this process, unlike in meiosis.

Area of Science:

  • Molecular Biology
  • Genetics
  • Yeast Biology

Background:

  • Chromosomal rearrangements can arise from ectopic homologous recombination between dispersed repetitive DNA.
  • Meiotic ectopic recombination in Schizosaccharomyces pombe (fission yeast) with dispersed ade6 heteroalleles often leads to chromosomal rearrangements.

Purpose of the Study:

  • To investigate mitotic ectopic recombination using the same substrates previously studied in meiosis.
  • To compare recombination rates and crossover frequencies between mitotic and meiotic recombination.
  • To identify potential diploid-specific factors that may regulate ectopic recombination.

Main Methods:

  • Utilized artificially dispersed ade6 heteroalleles in Schizosaccharomyces pombe.
  • Assessed ectopic recombination rates in both haploid and heterozygous diploid yeast strains during mitosis.
  • Quantified crossover frequencies associated with both allelic and ectopic recombination events in mitosis.

Main Results:

  • Mitotic ectopic recombination rates in haploids were comparable to allelic recombination rates in diploids (1-4 x 10^-6 recombinants/cell generation).
  • Ectopic recombination rates in heterozygous diploids were significantly lower (2.5-70 fold) than in haploids or compared to allelic recombination.
  • Mitotic recombination, both allelic and ectopic, showed very low crossover frequencies (2% for allelic, 1-7% for ectopic), contrasting sharply with meiotic recombination (35-65% crossovers).

Conclusions:

  • Diploid-specific factors likely inhibit mitotic ectopic recombination in Schizosaccharomyces pombe.
  • Mitosis and meiosis exhibit differential control over the resolution of recombination intermediates or employ alternative recombination pathways.
  • The low crossover frequency in mitotic recombination suggests distinct mechanisms compared to meiotic recombination.

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