Ascus definition

ăskəs
asci
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In ascomycetous fungi, a sac in which spores (usually eight) are produced and meiosis occurs.
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A membranous, often club-shaped structure inside which ascospores are formed through sexual reproduction in species of the fungi known as ascomycetes. The ascus is unique to ascomycetes and distinguishes them from other kinds of fungi. Asci are formed when two hyphae that are sexually compatible conjugate. Each ascus typically develops eight ascospores. Asci swell at maturity until they burst, shooting the ascospores into the air.
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A sac-shaped cell present in ascomycete fungi; it is a reproductive cell in which meiosis and an additional cell division produce eight spores.
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A membranous, often club-shaped structure in ascomycetes in which karyogamy occurs, followed by the formation of eight haploid ascospores.
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Other Word Forms

Noun

Singular:
ascus
Plural:
asci

Origin of ascus

  • New Latin from Greek askos bag

    From American Heritage Dictionary of the English Language, 5th Edition

  • From Ancient Greek ἀσκός (askos, “a sac”).

    From Wiktionary

Ascus Sentence Examples

  • According to his view, the ascus is in effect the sporangium with several spores, the conidium the sporangiole with but one spore, and that not loose but fused with the sporangiole wall.

  • The ascus is thus one of the most sharply characterized structures among the fungi.

  • In a few cases both among the higher and the lower plants, of which the formation of spores in the ascus is a typical example, new cells are formed by the aggregation of portions of the cytoplasm around the nuclei which become delimited from the rest of the cell iontents by a membrane.

  • Ascus from perithecium containing six spores, X30o.

  • In young asci a similar fusion of two nuclei occurs, and also in basidia, in each case the nucleus of the ascus or of the basidium resulting from the fusion subsequently giving rise by division to the nuclei of the ascospores and basidiospores respectively.

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