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An aster is a cellular structure shaped like a star, consisting of a centrosome and its associated microtubules during the early stages of mitosis in an animal cell. [1]: 221 Asters do not form during mitosis in plants. Astral rays, composed of microtubules, radiate from the centrosphere and look like a cloud. Astral rays are one variant of ...
3D rendering of centrioles showing the triplets. In cell biology a centriole is a cylindrical organelle composed mainly of a protein called tubulin. [1] Centrioles are found in most eukaryotic cells, but are not present in conifers (), flowering plants (angiosperms) and most fungi, and are only present in the male gametes of charophytes, bryophytes, seedless vascular plants, cycads, and Ginkgo.
The cellular spindle apparatus includes the spindle microtubules, associated proteins, which include kinesin and dynein molecular motors, condensed chromosomes, and any centrosomes or asters that may be present at the spindle poles depending on the cell type. [4] The spindle apparatus is vaguely ellipsoid in cross section and tapers at the ends.
The mother centriole just aids in the accumulation of materials required for the assembly of the daughter centriole. [17] Centrosome (shown by arrow) next to nucleus. Centrioles, however, are not required for the progression of mitosis. When the centrioles are irradiated by a laser, mitosis proceeds normally with a morphologically normal spindle.
A 3D diagram of a centriole. Each circle represents one microtubule. In total there are 27 microtubules organized into 9 bundles of 3. The centrosome is the main MTOC (microtubule organizing center) of the cell during mitosis. Each centrosome is made up of two cylinders called centrioles, oriented at right angles to each other. The centriole is ...
However, the two centrioles are of different ages. This is because one centriole originates from the mother cell while the other is replicated from the mother centriole during the cell cycle. It is possible to distinguish between the two preexisting centrioles because the mother and daughter centriole differ in both shape and function. [5]
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The family is commonly known as the aster, daisy, composite, or sunflower family. Most species of Asteraceae are herbaceous plants, and may be annual, biennial, or perennial, but there are also shrubs, vines, and trees. The family has a widespread distribution, from subpolar to tropical regions, in a wide variety of habitats.