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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 ...
Prophase is the first stage of mitosis in animal cells, and the second stage of mitosis in plant cells. [10] At the start of prophase there are two identical copies of each chromosome in the cell due to replication in interphase. These copies are referred to as sister chromatids and are attached by DNA element called the centromere. [11]
The centrosome is thought to have evolved only in the metazoan lineage of eukaryotic cells. [2] Fungi and plants lack centrosomes and therefore use other structures to organize their microtubules. [ 3 ] [ 4 ] Although the centrosome has a key role in efficient mitosis in animal cells, it is not essential in certain fly and flatworm species.
Chromosome segregation occurs at two separate stages during meiosis called anaphase I and anaphase II (see meiosis diagram). In a diploid cell there are two sets of homologous chromosomes of different parental origin (e.g. a paternal and a maternal set).
[1] γ-tubulin is a protein located at the centrosome that nucleates the microtubules by interacting with the tubulin monomer subunit in the microtubule at the minus end. [1] Organization of the microtubules at the MTOC, or centrosome in this case, is determined by the polarity of the microtubules defined by y-tubulin. [1]
Microtubule and tubulin metrics [1]. Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nm [2] and have an inner diameter between 11 and 15 nm. [3]
A new study says the flu A viral strain can adapt shape to stay infectious. Infectious disease doctors break down what this means and how to protect yourself.
The aster shouldn't be shown as sun rays; they should have the same appearance as the spindle microtubules (but shorter). The "Homologous chromosomes" label in prophase I should probably point to each of the pairs, the way "Sister chromatids" does in anaphase I. Typo in the anaphase I description: should be "chromosomes", not "chrmosomes".