<h2 class="section-header"><strong class="title">Mitotic Phase</strong></h2>
<p class="para">The mitotic phase (M phase) is composed of two tightly coupled processes: <em class="emphasis">mitosis</em> and <em class="emphasis">cytokinesis</em>. During mitosis the chromosomes in the cell nucleus separate into two identical sets in two nuclei. This is followed by <em class="emphasis">cytokinesis</em> in which the cytoplasm, organelles and cell membrane split into two cells containing roughly equal shares of these cellular components. We will now describe what takes place during the stages of M-phase, which includes the four broad phases of mitosis (prophase, metaphase, anaphase, telophase) and the fifth phase of cytokinesis:</p>
<div class="list">
<ol class="arabic">
<li class="item">prophase</li>
<li class="item">metaphase</li>
<li class="item">anaphase</li>
<li class="item">telophase</li>
<li class="item">cytokinesis</li>
</ol>
</div>
<h3 class="para">1. Prophase</h3>
<p class="para">During prophase, the <em class="emphasis">chromatin</em> material shortens and thickens into individual chromosomes which are visible under the light microscope. Each chromosome consist of two strands or <em class="emphasis">chromatids</em> joined by a <em class="emphasis">centromere</em> (see figure below).</p>
<div class="ns-tutorial">
<div class="ns-school-defn2">
<h3 class="note-header"><span class="cnx_label">Fact:</span></h3>
<p class="para">Human cells have 46 chromosomes. (23 from the mother and 23 from the father).</p>
</div>
</div>
<p class="para">As prophase progresses, the nuclear membrane and nucleolus disintegrates. In animal cells the <em class="emphasis">centrioles</em> separate and move to opposite poles. The centrioles give rise to the spindle fibres which form between the poles. In plant cells there are no centrioles to move to the poles, so spindle fibres form in the cytoplasm.</p>
<table>
<tbody>
<tr>
<td><b class="emphasis">Schematic Diagram</b>: Animal cell</td>
<td><b class="emphasis">Micrograph</b>: Plant cell</td>
</tr>
<tr>
<td><a href="https://data.ulearngo.com/assets/622f342e-03a0-4e27-aec5-69de1684ca15"><img alt="animal-cell-prophase" class="size-full wp-image-100293 alignnone" height="225" src="https://data.ulearngo.com/assets/622f342e-03a0-4e27-aec5-69de1684ca15" width="336"/></a></td>
<td><a href="https://data.ulearngo.com/assets/ce2e55bb-f26a-46e6-b6d0-19e5ebe1bed5"><img alt="plant-cell-prophase" class="size-full wp-image-100294 alignnone" height="200" src="https://data.ulearngo.com/assets/ce2e55bb-f26a-46e6-b6d0-19e5ebe1bed5" width="336"/></a></td>
</tr>
</tbody>
</table>
<h3 class="para">2. Metaphase</h3>
<p class="para">During metaphase, chromosomes line up on the <em class="emphasis">equator</em> of the cell. The chromosomes appear in a straight line across the middle of the cell. Each chromosome is attached to the spindle fibres by its centromere.</p>
<div class="ns-tutorial">
<div class="ns-school-defn2">
<h3 class="note-header"><span class="cnx_label">Note:</span></h3>
<p class="para"><em class="emphasis">HINT</em>: The stages of the cell cycle (<em class="emphasis">i</em>nterphase, <em class="emphasis">p</em>rophase, <em class="emphasis">m</em>etaphase, <em class="emphasis">a</em>naphase, <em class="emphasis">t</em>elophase) can be remembered by using the mnemonic <em class="emphasis">IPMAT</em>.</p>
</div>
</div>
<table>
<tbody>
<tr>
<td><b class="emphasis">Schematic Diagram</b>: Animal cell</td>
<td><b class="emphasis">Micrograph</b>: Plant cell</td>
</tr>
<tr>
<td><a href="https://data.ulearngo.com/assets/29abcfd1-d3b9-45b8-aa74-e3952952a354"><img alt="metaphase-animal-cell" class="size-full wp-image-100295 alignnone" height="221" src="https://data.ulearngo.com/assets/29abcfd1-d3b9-45b8-aa74-e3952952a354" width="336"/></a></td>
<td><a href="https://data.ulearngo.com/assets/1eb1cee9-1856-462b-8054-1654681a30ff"><img alt="metaphase-plant-cell" class="size-full wp-image-100296 alignnone" height="234" src="https://data.ulearngo.com/assets/1eb1cee9-1856-462b-8054-1654681a30ff" width="336"/></a></td>
</tr>
</tbody>
</table>
<h3 class="para">3. Anaphase</h3>
<p class="para">During anaphase the chromatids are pulled to opposite poles of the cell by the shortening of the spindle fibres. The chromatids are now called <em class="emphasis">daughter chromosomes</em>.</p>
<table>
<tbody>
<tr>
<td><b class="emphasis">Schematic Diagram</b>: Animal cell</td>
<td><b class="emphasis">Micrograph</b>: Plant cell</td>
</tr>
<tr>
<td><a href="https://data.ulearngo.com/assets/22dbcf29-19f0-490f-8896-302b8cb91887"><img alt="anaphase-animal-cell" class="size-full wp-image-100297 alignnone" height="196" src="https://data.ulearngo.com/assets/22dbcf29-19f0-490f-8896-302b8cb91887" width="336"/></a></td>
<td><a href="https://data.ulearngo.com/assets/ad748433-4cf4-4253-a5ef-8f370c5cad21"><img alt="anaphase-plant-cell" class="size-full wp-image-100298 alignnone" height="233" src="https://data.ulearngo.com/assets/ad748433-4cf4-4253-a5ef-8f370c5cad21" width="336"/></a></td>
</tr>
</tbody>
</table>
<div class="ns-tutorial">
<div class="ns-school-defn2">
<h3 class="note-header"><span class="cnx_label">Fact:</span></h3>
<p class="para">In plant cells there are no centrioles to move to the poles, so spindle fibres form in the cytoplasm.</p>
</div>
</div>
<h3 class="para">4. Telophase</h3>
<p class="para">During telophase, a nuclear membrane reforms around the daughter chromosomes that have gathered at each of the poles. The daughter chromosomes uncoil to form chromatin once again. The nuclear membrane reforms.</p>
<table>
<tbody>
<tr>
<td><b class="emphasis">Schematic Diagram</b>: Animal cell</td>
<td><b class="emphasis">Micrograph</b>: Plant cell</td>
</tr>
<tr>
<td><a href="https://data.ulearngo.com/assets/a2bb4546-f5f4-484f-8600-6fe860605fb7"><img alt="telophase-animal-cell" class="size-full wp-image-100299 alignnone" height="172" src="https://data.ulearngo.com/assets/a2bb4546-f5f4-484f-8600-6fe860605fb7" width="336"/></a></td>
<td><a href="https://data.ulearngo.com/assets/b8d38827-e108-4624-a319-32916998a455"><img alt="telophase-plant-cell" class="size-full wp-image-100300 alignnone" height="217" src="https://data.ulearngo.com/assets/b8d38827-e108-4624-a319-32916998a455" width="336"/></a></td>
</tr>
</tbody>
</table>
<h3 class="para">5. Cytokinesis</h3>
<p class="para">The cytoplasm then divides during a process called <em class="emphasis">cytokinesis</em>. Cytokinesis is not a stage of mitosis but the process of the cytoplasm splitting into two. In an animal cell the cell membrane constricts. This <em class="emphasis">invagination</em> or in-folding of the cytoplasm divides the cell in two. In a plant cell a <em class="emphasis">cross wall</em> is formed by the <em class="emphasis">cell plate</em> dividing the cytoplasm in two.</p>
<table>
<tbody>
<tr>
<td colspan="2"><b class="emphasis">Schematic Diagram</b>: Animal Cell</td>
<td><b class="emphasis">Micrograph</b></td>
</tr>
<tr>
<td><a href="https://data.ulearngo.com/assets/4cc5ca4e-4e7f-4b9c-bbf8-1008edb11783"><img alt="cytokinesis-1" class="size-full wp-image-100302 alignnone" height="131" src="https://data.ulearngo.com/assets/4cc5ca4e-4e7f-4b9c-bbf8-1008edb11783" width="168"/></a> </td>
<td><a href="https://data.ulearngo.com/assets/45369a0a-6d17-40a9-9f2e-e4c528042ff2"><img alt="cytokinesis-2" class="size-full wp-image-100303 alignnone" height="131" src="https://data.ulearngo.com/assets/45369a0a-6d17-40a9-9f2e-e4c528042ff2" width="168"/></a> </td>
<td><a href="https://data.ulearngo.com/assets/0975cc9b-1cda-4a95-b43f-199fa5183718"><img alt=" cytokinesis-micrograph" class="size-full wp-image-100304 alignnone" height="203" src="https://data.ulearngo.com/assets/0975cc9b-1cda-4a95-b43f-199fa5183718" width="336"/></a></td>
</tr>
</tbody>
</table>
<p class="para">There are now two <em class="emphasis">genetically identical</em> daughter cells which are identical to the parent cell and to each other.</p>
<h2>Summary Video: Mitosis</h2>
<p>The <a href="http://www.amoebasisters.com/">Amoeba Sisters</a> video below walks you through the reason for mitosis with mnemonics for prophase, metaphase, anaphase, and telophase. </p>
<p><iframe allowfullscreen="allowfullscreen" frameborder="0" height="360" src="https://www.youtube.com/embed/f-ldPgEfAHI?rel=0&amp;modestbranding=1&amp;cc_lang_pref=en&amp;cc_load_policy=1" width="640"></iframe></p>

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Mitotic Phase

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Mitotic Phase

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