Contents 1 Chromosome silencing 2 Recombination 3 References 4 External links

Chromosome silencing[edit] In mammals, surveillance mechanisms remove meiotic cells in which synapsis is defective. One such surveillance mechanism is meiotic silencing that involves the transcriptional silencing of genes on asynapsed chromosomes.[4] Any chromosome region, either in males or females, that is asynapsed is subject to meiotic silencing.[5] ATR, BRCA1 and gammaH2AX localize to unsynapsed chromosomes at the pachytene stage of meiosis in human oocytes and this may lead to chromosome silencing.[6] The DNA damage response protein TOPBP1 has also been identified as a crucial factor in meiotic sex chromosome silencing.[4] DNA double-strand breaks appear to be initiation sites for meiotic silencing.[4]

Recombination[edit] In female Drosophila melanogaster fruit flies, meiotic chromosome synapsis occurs in the absence of recombination.[7] Thus synapsis in Drosophila is independent of meiotic recombination, consistent with the view that synapsis is a precondition required for the initiation of meiotic recombination. Meiotic recombination is also unnecessary for homologous chromosome synapsis in the nematode Caenorhabditis elegans.[8]

References[edit] ^ Revenkova E, Jessberger R (2006). "Shaping meiotic prophase chromosomes: cohesins and synaptonemal complex proteins" (PDF). Chromosoma. 115 (3): 235–40. doi:10.1007/s00412-006-0060-x. PMID 16518630.  ^ 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 (2006). "Sex chromosomes, synapsis, and cohesins: a complex affair" (PDF). Chromosoma. 115 (3): 250–9. doi:10.1007/s00412-006-0059-3. PMID 16544151.  ^ McKee B (2004). "Homologous pairing and chromosome dynamics in meiosis and mitosis". Biochim Biophys Acta. 1677 (1-3): 165–80. doi:10.1016/j.bbaexp.2003.11.017. PMID 15020057.  ^ a b c ElInati E, Russell HR, Ojarikre OA, Sangrithi M, Hirota T, de Rooij DG, McKinnon PJ, Turner JM (2017). "DNA damage response protein TOPBP1 regulates X chromosome silencing in the mammalian germ line". Proc. Natl. Acad. Sci. U.S.A. 114 (47): 12536–12541. doi:10.1073/pnas.1712530114. PMID 29114052.  ^ Turner JM (2015). "Meiotic Silencing in Mammals". Annu. Rev. Genet. 49: 395–412. doi:10.1146/annurev-genet-112414-055145. PMID 26631513.  ^ Garcia-Cruz R, Roig I, Robles P, Scherthan H, Garcia Caldés M (2009). "ATR, BRCA1 and gammaH2AX localize to unsynapsed chromosomes at the pachytene stage in human oocytes". Reprod. Biomed. Online. 18 (1): 37–44. PMID 19146767.  ^ McKim KS, Green-Marroquin BL, Sekelsky JJ, Chin G, Steinberg C, Khodosh R, Hawley RS (1998). "Meiotic synapsis in the absence of recombination". Science. 279 (5352): 876–8. PMID 9452390.  ^ Dernburg AF, McDonald K, Moulder G, Barstead R, Dresser M, Villeneuve AM (1998). "Meiotic recombination in C. elegans initiates by a conserved mechanism and is dispensable for homologous chromosome synapsis". Cell. 94 (3): 387–98. PMID 9708740. 

External links[edit] Look up synapsis in Wiktionary, the free dictionary. UC Berkeley video of chromosome end migration and match assessment during prophase This cell biology article is a stub. You can help Wikipedia by expanding it. v t e Retrieved from "" Categories: Cell biologyCytogeneticsCell biology stubsHidden categories: All stub articles

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