Synapsis 2991457 221298270 2008-06-23T22:28:28Z DWeissman 1993114 deleted the last line, which linked to a page on logical disjunction {{Wiktionary|synapsis}} '''Synapsis''' (also called '''syndesis''') is the pairing of two [[homologous chromosome]]s that occurs during [[meiosis]].<ref>{{cite journal |author=McKee B |title=Homologous pairing and chromosome dynamics in meiosis and mitosis |journal=Biochim Biophys Acta |volume=1677 |issue=1-3 |pages=165–80 |year=2004 |pmid=15020057}}</ref> It is a form of [[chromosomal crossover]]. Synapsis takes place during prophase I. When homologous chromosomes synapse, they come closer together until they are connected by a protein complex called the [[synaptonemal complex]], which contains central and lateral elements.<ref>{{cite journal |author=Revenkova E, Jessberger R |title=Shaping meiotic prophase chromosomes: cohesins and synaptonemal complex proteins |url=http://www.springerlink.com/content/fm26j18850w2762t/fulltext.pdf |journal=Chromosoma |volume=115 |issue=3 |pages=235–40 |year=2006 |pmid=16518630 |doi=10.1007/s00412-006-0060-x}}</ref> While [[autosome]]s undergo synapsis during meiosis [[sex chromosome]]s usually remain unpaired.<ref>{{cite journal |author=Page J, de la Fuente R, Gómez R, Calvente A, Viera A, Parra M, Santos J, Berríos S, Fernández-Donoso R, Suja J, Rufas J |title=Sex chromosomes, synapsis, and cohesins: a complex affair |url=http://www.springerlink.com/content/1683677374l40532/fulltext.pdf |journal=Chromosoma |volume=115 |issue=3 |pages=250–9 |year=2006 |pmid=16544151 |doi=10.1007/s00412-006-0059-3}}</ref> When the non-sister chromatids intertwine, segments of chromatids with the same sequence break apart at and are exchanged in a process known as [[genetic recombination]] or "crossing-over". Recombination exchanges genetic material between homologous chromosomes and increases the genetic variability of the offspring. This exchange produces a [[chiasma]], a region that is shaped like an X, where the two chromosomes are physically joined. ==References== {{reflist}} [[Category:Cell biology]][[Category:Cytogenetics]] {{Cell-biology-stub}} [[fr:Synapsis]] [[pt:Synapsis]]