Global InformationAchiasmate Meiosis information
Achiasmate Meiosis refers to meiosis without chiasmata, which are structures that are necessary for recombination to occur and that usually aid in the segregation of non-sister homologs.[1] The pachytene stage of prophase I typically results in the formation of chiasmata between homologous non-sister chromatids in the tetrad chromosomes that form.[1] The formation of a chiasma is also referred to as crossing over. When two homologous chromatids cross over, they form a chiasma at the point of their intersection. However, it has been found that there are cases where one or more pairs of homologous chromosomes do not form chiasmata during pachynema.[2][3][4] Without a chiasma, no recombination between homologs can occur.
The traditional line of thinking was that without at least one chiasma between homologs, they could not be properly segregated during metaphase because there would be no tension between the homologs for the microtubules to pull against.[5] This tension between the homologs is typically what allows the chromosomes to align along an axis of the cell (the metaphase plate) and to then properly segregate to opposite sides of the cell. Despite this, achiasmate homologs are still found to line up with the chiasmate chromosomes at the metaphase plate.[6]
- ^ a b King, Robert C. (2013). A dictionary of genetics. Pamela Khipple Mulligan, William D. Stansfield (8th ed.). New York: Oxford University Press. ISBN 978-0-19-937686-5. OCLC 871046520.
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:5was invoked but never defined (see the help page). - ^ Wolf, Klaus Werner (February 1994). "How meiotic cells deal with non-exchange chromosomes". BioEssays. 16 (2): 107–114. doi:10.1002/bies.950160207. ISSN 0265-9247. PMID 8147841. S2CID 32544159.
- ^ Bosco, Giovanni (2009-02-06). Copenhaver, Gregory P. (ed.). "When Segregation Hangs by a Thread". PLOS Genetics. 5 (2): e1000371. doi:10.1371/journal.pgen.1000371. ISSN 1553-7404. PMC 2631148. PMID 19197362.