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Mitosis: The Division of Cells
Q1: How do cells divide? If a cell splits in half to become two cells how are both those able to work?
A1: The cell's chromosomes duplicate themselves, then both of them move to opposite cell walls. The cell elongates and it's plasma membrane grows inward, then the cell splits! The cell divides and creates two sister cells. Those sister cells are able to work because the mother cell gives them everything they need to produce and survive.
Q2: Write a brief description of what is happening at each of the seven stages of cell division starting with Interphase.
A2: 1. Interphase- This is the longest part of the complete cell cycle. The cell is very active while the DNA replicates, centrioles divide, and proteins are being made.
2. Prophase- During the first stage of mitosis, the nucleolus fades and replicated (copied) DNA and associated proteins, also called the chromatin, condenses into the chromosomes. Each one of these chromosomes has two chromatids, and all of those chromatids have the same genetic information. The microtubules of the cytoskeleton also disassemble.
3. Prometaphase- the nuclear envelope collapses in this stage so there is no longer a recognizable nucleus. Some spindle fibers connect to chromosomes, but others elongate and and overlap each other at the cell center.
4. Metaphase- Tension applied by the spindle fibers aligns all chromosomes in one plane at the center of the cell.
5. Anaphase- Spindle fibers shorten, the kinetochores separate, and the daughter chromosomes, also called chromatids, are pulled apart and begin moving to the cell poles.
6. Telophase- The daughter chromosomes arrive at the poles and the spindle fibers that have pulled them apart disappear.
7. Cytokinesis- the spindle fibers that didn't attach themselves to chromosomes start breaking down until only a small portion of the overlap is left. Also in this region, a contractile ring finally separates the cell into two sister cells. Microtubules in both of those cells then reorganize themselves into a new cytoskeleton for the return of cell interphase.
Article posted January 25, 2012 at 11:53 AM •
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