High-resolution mapping of meiotic crossovers and non-crossovers in yeast.
Meiotic recombination has a central role in the evolution of sexually reproducing organisms. The two recombination outcomes, crossover and non-crossover, increase genetic diversity, but have the potential to homogenize alleles by gene conversion. Whereas crossover rates vary considerably across the genome, non-crossovers and gene conversions have only been identified in a handful of loci. To examine recombination genome wide and at high spatial resolution, we generated maps of crossovers, crossover-associated gene conversion and non-crossover gene conversion using dense genetic marker data collected from all four products of fifty-six yeast (Saccharomyces cerevisiae) meioses. Our maps reveal differences in the distributions of crossovers and non-crossovers, showing more regions where either crossovers or non-crossovers are favoured than expected by chance. Furthermore, we detect evidence for interference between crossovers and non-crossovers, a phenomenon previously only known to occur between crossovers. Up to 1% of the genome of each meiotic product is subject to gene conversion in a single meiosis, with detectable bias towards GC nucleotides. To our knowledge the maps represent the first high-resolution, genome-wide characterization of the multiple outcomes of recombination in any organism. In addition, because non-crossover hotspots create holes of reduced linkage within haplotype blocks, our results stress the need to incorporate non-crossovers into genetic linkage analysis.
Mancera
Eugenio
E
European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
Bourgon
Richard
R
Brozzi
Alessandro
A
Huber
Wolfgang
W
Steinmetz
Lars M
LM
D002874:Chromosome Mapping; D015825:Chromosomes, Fungal / Q000235:genetics; D003434:Crossing Over, Genetic / Q000235:genetics*; D053903:DNA Breaks, Double-Stranded; D004268:DNA-Binding Proteins / Q000235:genetics; D045585:Flap Endonucleases; D005785:Gene Conversion / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal; D008040:Genetic Linkage / Q000235:genetics; D005819:Genetic Markers / Q000235:genetics; D016681:Genome, Fungal / Q000235:genetics; D005838:Genotype; D006239:Haplotypes / Q000235:genetics; D008540:Meiosis / Q000235:genetics*; D009154:Mutation / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics; D015534:Trans-Activators / Q000235:genetics
D004268:DNA-Binding Proteins; D005819:Genetic Markers; C091158:MSH4 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D045585:Flap Endonucleases; C112337:MMS4 protein, S cerevisiae