A current model of meiotic recombination, initiated by a double-strand break or gap, followed by pairing with an homologous chromosome and strand invasion to initiate the recombinational repair process.  Repair of the gap can lead to crossover (CO) or non-crossover (NCO) of the flanking regions.  CO recombination is thought to occur by the Double Holliday Junction (DHJ) model, illustrated on the right, above.  NCO recombinants are thought to occur primarily by the Synthesis Dependent Strand Annealing (SDSA) model, illustrated on the left, above.  Most recombination events appear to be the SDSA type.
Harris Bernstein, Carol Bernstein and Richard E. Michod
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Meiosis as an Evolutionary Adaptation for DNA Repair. Chapter 19 in DNA Repair. Inna Kruman editor. InTech Open Publisher. DOI: 10.5772/25117 <a rel="nofollow" class="external free" href="http://www.intechopen.com/books/dna-repair/meiosis-as-an-evolutionary-adaptation-for-dna-repair">http://www.intechopen.com/books/dna-repair/meiosis-as-an-evolutionary-adaptation-for-dna-repair</a>