Tag: Yeast
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ASCUS (Formerly Theca)
This article is about the spore-bearing cell in fungi. For Atypical Squamous Cells of Undetermined Significance (ASCUS), see Bethesda system. For the Greek mythological giant, see Ascus (mythology). (pl. asci) a cell present in the fruiting body of ASCOMYCETE fungi in which the fusion of HAPLOID nuclei occurs during sexual reproduction. This is normally followed by MEIOSIS, giving rise to four haploid cells, after which MITOSIS produces eight ASCOSPORES. The precise arrangement of ascospores within the ascus enables the events at meiosis to be fully analysed (see TETRAD ANALYSIS). The asci are usually enclosed within an aggregation of hyphae termed an ASCOCARP, a number of different types being recognized, e.g. perithecium, cleistothecium, apothecium. (Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005) An ascus (from Ancient Greek ἀσκός (askós) ‘skin bag, wineskin’; pl.: asci)[1] is the sexual spore-bearing cell produced in ascomycete fungi. Each ascus usually contains eight ascospores (or octad), produced by meiosis followed, in most species, by a mitotic cell division. However, asci in some genera…