© Christine MEZARD / INRA / CNRS Images
Initial phase of fertilisation in Arabidopsis thaliana, or mouse-ear cress, observed using a scanning microscope. A tetrad of pollen grains has been deposited onto the stigmatic papillae of a pistil. It can be seen that two of these grains are starting to germinate. Next, the pollen grains will form a pollen tube that will insert itself into the pistil to bring the sperm nucleus into contact with the ovule nucleus. Through these experiments, research scientists study meiosis, the specialised type of cell division that enables reproduction through the production of gametes. This phenomenon is accompanied by the homologous recombination of homologous chromosomes, which leads to genetic exchange or crossover, thereby producing new allele combinations in the next generation. Comparative analysis of the genomes from the four plants obtained after fertilisation by the four pollen grains in a tetrad makes it possible to reconstruct the history of homologous recombination events during a single case of meiosis.