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Aded all along chromosomes before or throughout S phase and establishes cohesion in the course of DNA replication.2,five The core cohesin components are two lengthy coiledcoil proteins, SMC1 and SMC3, which interact with each other and with a "kleisin" subunit (SCC1/Rad21 in mitosis) to form a tripartite ring, and SCC3/SA/Stromalin, which attaches towards the kleisin component and mediates a variety of interactions. The primary removal pathway at anaphase entails cleavage on the kleisin subunit by the protease enzyme Separase. Meiotic cohesins seem to possess the same fundamental subunit composition but 1 or far more with the core subunits may be replaced by a meiosis-specific paralog. Most such variants are restricted to fairly narrow taxonomic ranges and their distinct functions will not be well-characterized but the meiosis-specific kleisin Rec8 replaces SCC1/Rad21 in most meiotic cohesins in almost all eukaryotes.two,6-8 We are going to look at the unique properties of Rec8 below.Bi-orientation of homologs and chiasmata. Homologous chromosomes should bi-orient at meiosis I (Fig. 1). Even though every homolog consists of a pair of sister chromatids held together by cohesion, that cohesion alone is of no use because it does not connect homologs. two Instead, the homolog connectors for most eukaryotes are "chiasmata" in which crossovers among homologous chromatids are stabilized by cohesion in between the crossover chromatids and their sisters distal to the crossover sites (Fig. 1).9 These connections avert homologs from dissociating prior to anaphase I, a significant lead to of nondisjunction and aneuploidy. Furthermore, during prometaphase I and metaphase I, chiasmata give the resistance that enables homolog pairs to achieve bipolar orientation on the meiosis I spindle. Activation of Separase at anaphase I causes dissolution of chiasmata (Fig. 1), therefore TH-302 In Vitro releasing homologs to segregate. two Formation of chiasmata is really a complex process that encompasses three key methods: homolog pairing and alignment; ten synapsis (formation of synaptonemal complexes (SC)s, an elaborate protein network that serves because the interface involving paired homologs); 11 and meiotic recombination, a specialized version on the double strand break repair pathway biased toward use of homologous chromatids as repair templates.12 TheseSpermatogenesisVolume two Issueprocesses have been the concentrate of most meiosis study but, using the exception of homolog pairing, will not be additional discussed since they play no part in Drosophila male meiosis. Centromere orientation. As indicated above, bi-orientation needs a pair of appropriately organized kinetochores capable of binding to microtubule bundles originating from opposite poles. In mitosis and meiosis II, sister kinetochores adopt a "back-toback" orientation and are normally visibly separate and stretched toward the poles through prometaphase I. During meiosis I, a important prerequisite for bipolar orientation of homologs is "mono-orientation" (or "co-orientation") of sister centromeres, in which sister centromeres type a functionally single kinetochore and orient for the similar pole2,13 (Fig. 1). If not for this behavior, there would be four functionally independent centromeres/kinetochores in each bivalent but only two poles, a recipe for segregational chaos. In ultrastructural research of meiosis I centromeres from several different eukaryotes, the kinetochore forming regions on the sister centromeres seem fused during prophase I but turn out to be resolved by anaphase I.14-16 This has led to the thought that sister ce.