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Typically, a single ascus will contain eight ascospores (or octad). The eight spores are produced by meiosis followed by a mitotic division. Two meiotic divisions turn the original diploid zygote nucleus into four haploid ones. That is, the single original diploid cell from which the whole process begins contains two complete sets of chromosomes.
The ascus itself forms as a radiating spur branch at the top of the hook. Each nucleus divides, resulting in the formation of a pair of compatible nuclei, i.e. a dikaryon, in the ascus, which is now the penultimate space. Two sister nuclei remain, one in the basal cell and the other in the crozier tip.
There are 2000 identified genera and 30,000 species of Ascomycota. The unifying characteristic among these diverse groups is the presence of a reproductive structure known as the ascus, though in some cases it has a reduced role in the life cycle. Many ascomycetes are of commercial importance.
The generic name polyascus (poly "many" + ascus "bag") refers to the typical presence of multiple external sac-like female bodies, known as externae. In Polyascus species, these originate from asexual reproduction.
The eight ascospores are produced inside an ascus. Sordaria squashes can give us information about crossing over during meiosis. If no crossing over occurs a 4:4 pattern is produced: four black spores, and four tan spores all lined up. If crossing over does occur there is a 2:2:2:2 pattern visible, or a 2:4:2 pattern.
Ascus (Ancient Greek: Ἄσκος) was a giant from ancient Greek mythology, who in conjunction with Lycurgus of Thrace chained the god Dionysus and threw him into a river. The god Hermes (or, according to other tellings, Zeus ) rescued Dionysus, conquered (ἐδαμασεν) the giant, flayed him, and made a bag (ἄσκος) of his skin.
As of February 2017, there were more than 400 hours of content uploaded to YouTube each minute, and one billion hours of content being watched on YouTube every day. As of October 2020, YouTube is the second-most popular website in the world, behind Google, according to Alexa Internet. [1]
The most popular video hosting website is YouTube, 2 billion active until October 2020 and the most extensive catalog of online videos. [1] There are some countries in the world placing restrictions on YouTube , instead having their own regional video-sharing websites in its place.