Summary: The eukaryotic recombinases RAD51 and DMC1 are essential for DNA strand‐exchange between homologous chromosomes during meiosis. RAD51 is also expressed during mitosis, and mediates homologous recombination (HR) between sister chromatids. It has been suggested that DMC1 might be involved in the switch from intersister chromatid recombination in somatic cells to interhomolog meiotic recombination. At meiosis, the Arabidopsis Atrad51 null mutant fails to synapse and has extensive chromosome fragmentation. The Atdmc1 null mutant is also asynaptic, but in this case chromosome fragmentation is absent. Thus in plants, AtDMC1 appears to be indispensable for interhomolog homologous recombination, whereas AtRAD51 seems to be more involved in intersister recombination. In this work, we have studied a new AtRAD51 knock‐down mutant, Atrad51‐2, which expresses only a small quantity of RAD51 protein. Atrad51‐2 mutant plants are sterile and hypersensitive to DNA double‐strand break induction, but their vegetative development is apparently normal. The meiotic phenotype of the mutant consists of partial synapsis, an elevated frequency of univalents, a low incidence of chromosome fragmentation and multivalent chromosome associations. Surprisingly, non‐homologous chromosomes are involved in 51% of bivalents. The depletion of AtDMC1 in the Atrad51‐2 background results in the loss of bivalents and in an increase of chromosome fragmentation. Our results suggest that a critical level of AtRAD51 is required to ensure the fidelity of HR during interchromosomal exchanges. Assuming the existence of asymmetrical DNA strand invasion during the initial steps of recombination, we have developed a working model in which the initial step of strand invasion is mediated by AtDMC1, with AtRAD51 required to check the fidelity of this process.

Currently, food allergies are an important health concern worldwide. The presence of undeclared allergenic ingredients or the presence of traces of allergens due to accidental contamination during food processing poses a great health risk to sensitized individuals. Therefore, reliable analytical methods are required to detect and identify allergenic ingredients in food products. Real-time PCR allowed a specific and accurate amplification of allergen sequences. Some processing methods could induce the fragmentation and/or degradation of genomic DNA and some studies have been performed to analyze the effect of processing on the detection of different targets, as thermal treatment, with and without applying pressure. In this review, we give an updated overview of the applications of real-time PCR for the detection of allergens of tree nut in processed food products. The different variables that contribute to the performance of PCR methodology for allergen detection are also review and discussed.