During meiosis programmed DNA double-strand breaks (DSBs) are repaired by homologous recombination using the sister chromatid or the homologous chromosome (homolog) as a template. This repair results in crossover (CO) and non-crossover (NCO) recombinants. Only CO formation between homologs provides the physical linkages guiding correct chromosome segregation, which are essential to produce heal...

The eukaryotic RecA homologue Rad51 is a key factor in homologous recombination and recombinational repair. Rad51-like proteins have been identified from yeast (Rad55, Rad57 and Dmc1) to vertebrates (Rad51B, Rad51C, Rad51D, Xrcc2, Xrcc3 and Dmc1). These Rad51-like proteins are all members of the genetic recombination and DNA damage repair pathways. The sequenced genome of Arabidopsis thaliana e...

Formation of crossovers between homologous chromosomes during meiosis is positively regulated by the ZMM proteins (also known as SIC proteins). DNA damage checkpoint proteins also promote efficient formation of interhomolog crossovers. Here, we examined, in budding yeast, the meiotic role of the heterotrimeric DNA damage response clamp composed of Rad17, Ddc1 and Mec3 (known as '9-1-1' in other...

Defects in meiotic recombination in many organisms result in arrest because of activation of a meiotic checkpoint(s). The proximal defect that triggers this checkpoint in mammalian germ cells is not understood, but it has been suggested to involve either the presence of DNA damage in the form of unrepaired recombination intermediates or defects in homologous chromosome pairing and synapsis inde...

During meiosis DNA double-strand breaks initiate recombination in the distantly related budding and fission yeasts and perhaps in most eukaryotes. Repair of broken meiotic DNA is essential for formation of viable gametes. We report here distinct but overlapping sets of proteins in these yeasts required for formation and repair of double-strand breaks. Meiotic DNA breakage in Schizosaccharomyces...

In the present study, we demonstrate that minimal concentrations of retinoic acid (RA) (≤1 nM), equivalent to the quantity contaminating serum-containing culture media, are sufficient to promote meiotic entry and progression through meiotic prophase I (MPI) stages in isolated 12.5 days postcoitum (dpc) XX and XY mouse primordial germ cells (PGCs) in culture. Similar very low RA concentrations w...

Genetic analysis of fission yeast suggests a role for the spHop2-Mnd1 proteins in the Rad51 and Dmc1-dependent meiotic recombination pathways. In order to gain biochemical insights into this process, we purified Schizosaccharomyces pombe Hop2-Mnd1 to homogeneity. spHop2 and spMnd1 interact by co-immunoprecipitation and two-hybrid analysis. Electron microscopy reveals that S. pombe Hop2-Mnd1 bin...

Recombination during meiosis in the form of crossover events promotes the segregation of homologous chromosomes by providing the only physical linkage between these chromosomes. Recombination occurs not only between allelic sites but also between non-allelic (ectopic) sites. Ectopic recombination is often suppressed to prevent non-productive linkages. In this study, we examined the effects of v...

During meiosis, homologous chromosomes recognize each other, align, and exchange genetic information. This process requires the action of RecA-related proteins Rad51 and Dmc1 to catalyze DNA strand exchanges. The Mnd1-Hop2 complex has been shown to assist in Dmc1-dependent processes. Furthermore, higher eukaryotes possess additional RecA-related proteins, like XRCC3, which are involved in meiot...

Based on homologies between the yeast DMC1 and the lily LIM15 meiosis-specific genes, degenerate PCR primers were designed that amplified the Arabidopsis DMC1 gene (AtDMC1). AtDMC1 genomic DNA (8 kb) was sequenced, and the transcript was characterized by reverse transcriptase-polymerase chain reaction (RT-PCR) and by 5' and 3' RACE (rapid amplification of cDNA ends). The AtDMC1 gene contains 15...