Meiosis is a specialized type of cell division leading to the production of gametes. During meiotic prophase I, homologous chromosomes interact with each other and form bivalents (pairs of homologous chromosomes).
Three major meiotic processes—chromosome pairing, synapsis and recombination—are involved in the formation of bivalents.
Chromosome pairing is largely dependent on the initiation and progression of recombination in fungi, mammals and plants, but not in Caenorhabditis elegans or Drosophila. Synapsis and recombination are also tightly linked.
References
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Gerton JL, Hawley RS. Homologous chromosome interactions in meiosis: diversity amidst conservation. Nat Rev Genet. 2005 Jun;6(6):477-87. PMID: 15931171
Gudmundsdottir K, Ashworth A. BRCA2 in meiosis: turning over a new leaf. Trends Cell Biol. 2004 Aug;14(8):401-4. PMID: 15308204