Mitosis
Technically, mitosis is specifically the process of division of the chromosomes, while cytokinesis is officially the process of division of the cytoplasm to form two cells. In most cells, cytokinesis follows or occurs along with the last part of mitosis.
CentrioleRemember centrioles? They consist of nine sets of three microtubules, occur in animal cells only, and are involved in division of the chromosomes. Each animal cell has a pair of centrioles located just outside the nucleus. The two centrioles in the pair are oriented at right angles to each other. Just before mitosis, the centrioles replicate, so the cell now has four (two sets of two) as it starts mitosis.
CentrioleRemember centrioles? They consist of nine sets of three microtubules, occur in animal cells only, and are involved in division of the chromosomes. Each animal cell has a pair of centrioles located just outside the nucleus. The two centrioles in the pair are oriented at right angles to each other. Just before mitosis, the centrioles replicate, so the cell now has four (two sets of two) as it starts mitosis.
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Prophase:• Chromosomes become more coiled and can be viewed under a light microscope.
• Each duplicated chromosome is seen as a pair of sister chromatids joined by the duplicated but unseparated centromere.
• The nucleolus disappears during prophase.
• In the cytoplasm, the mitotic spindle, consisting of microtubules and other proteins, forms between the two pairs of centrioles as they migrate to opposite poles of the cell.
• The nuclear envelope disappears at the end of prophase. This signals the beginning of the substage called prometaphase.
Metaphase:• The
centrosomes are at opposite poles of the cell.
• The chromosomes, now at their most highly coiled and condensed, become arranged on a plane equidistant from the two poles called the metaphase plate.
• For each chromosome, the kinetochores of the sister chromatids face the opposite poles, and each is attached to a kinetochore microtubule coming from that pole.
• The chromosomes, now at their most highly coiled and condensed, become arranged on a plane equidistant from the two poles called the metaphase plate.
• For each chromosome, the kinetochores of the sister chromatids face the opposite poles, and each is attached to a kinetochore microtubule coming from that pole.
Anaphase:•
Anaphase begins when the duplicated centromeres of each pair of sister chromatids
separate, and the now-daughter chromosomes begin moving toward opposite poles
of the cell due to the action of the spindle.
• Depending where the centromere is located along the chromosome, a characteristic shape appears during chromosome movement. The two shown above give V and J shapes.
• At the end of anaphase, a complete set of chromosomes has assembled at each pole of the cell.
• Depending where the centromere is located along the chromosome, a characteristic shape appears during chromosome movement. The two shown above give V and J shapes.
• At the end of anaphase, a complete set of chromosomes has assembled at each pole of the cell.
Telophase:• The
chromosomes assemble in sets at the two poles.
• The chromosomes begin to uncoil and eventually assume the extended state characteristic of interphase.
• A nuclear envelope reforms around each chromosome set, the spindle disappears, and the nucleolus reforms. Nuclear division by mitosis is complete at this point.
• Cytokinesis, the division of the cytoplasm, usually is in progress before nuclear division is complete. In animal cells, cytokinesis involves the formation of a cleavage furrow resulting in the pinching of the cell into two.
• In some specialized cases, such as in the development of the Drosophila embryo, nuclear division occurs without being followed by cytokinesis.
• The chromosomes begin to uncoil and eventually assume the extended state characteristic of interphase.
• A nuclear envelope reforms around each chromosome set, the spindle disappears, and the nucleolus reforms. Nuclear division by mitosis is complete at this point.
• Cytokinesis, the division of the cytoplasm, usually is in progress before nuclear division is complete. In animal cells, cytokinesis involves the formation of a cleavage furrow resulting in the pinching of the cell into two.
• In some specialized cases, such as in the development of the Drosophila embryo, nuclear division occurs without being followed by cytokinesis.