3.7. Mitosis

• Interphase is the longest stage in the eukaryotic cell cycle
• Interphases purpose is to prepare the cell for division, which occurs later on in the cell cycle
• Gap One: the cell performs its normal functions and grows and continues to replicate organelles as normal. Proteins produced from which organelles will be synthesised
• S Phase: also known as synthesis, and this is when the DNA replicates. The DNA is "unzipped" by numerous proteins. Polymerase enzymes create new strands to pair with each half of the DNA
• Synthesis: produces sister chromatids which means that two identical daughter cells will form in mitosis
• G2: Gap two, is the last stage of interphase, where the cell adds volume to its cytoplasm while replicating important organelles
• In animals, mitochondria is replicated the most during gap 2 so that the cell has plenty of energy for mitosis to take place
• In plants, chloroplasts and mitochondria are replicated the most during interphase, gap two
• Prophase: The first stage of mitosis. Interphase isn't regarded as the first stage because it is just preparing the cell
• Prophase, chromatins condense into chromosomes and becomes visible in the nucleus. The nucleolus dissolves and disappears. The two centrioles created in G2 start moving to opposite poles of the cell
• Once the centrioles are at opposite ends, they begin to form spindle fibres, made out of protein microtubules.
• The spindle fibres then attach to the centromere of the chromosomes and begin to move them to the centre of the cell. The nuclear membrane then also starts to break down
• Once the nuclear envelope breaks down, the chromosomes are free in the cytoplasm
• Metaphase: the second stage of cell division, between prophase and anaphase, during which the chromosomes become attached to the spindle fibres.
• Each chromatid is an identical copy of DNA from the parent cell
• Metaphase: The chromosomes are pulled into the equator of the cell, making them equidistant to the centrosome poles
• Anaphase: The centromeres divide into two and the spindle fibres pull the chromatids apart.
• Anaphase: The separated chromatids then make their way to the opposite ends of the cell and are now called chromosomes.
• The energy for the stage anaphase is provided by the mitochondria, which gathers around the spindle fibres
• If cells are treated with chemicals that destroy the spindles, the chromosomes remain at the equator meaning they’re unable to reach the poles
• The replication of DNA takes place during interphase before the nucleus and cell divide
• Anaphase takes about 77.8 minutes to complete
• Telophase: The chromatids uncoil, becoming long and thin again. The spindle apparatus breaks down and the nuclear envelope reforms around the chromosomes.
• Telophase: The nucleous also reforms in each nucleus. The cell then begins to prepare to split the cytoplasm and its contents
• Telophase marks the conclusion of cell division. A successful completion of telophase ensures that genetic material has been properly distributed to the two daughter cells.
• Cyto: Cell
• Kinesis: Movement or motion
• Cytokinesis takes place in both eukaryotic and prokaryoic cells.
• Cytokinesis: The division of the cytoplasm into two daughter cells. It occurs at roughly the same time as telophase so both are considered to be one stage
• Cell division in prokaryotic cells is called binary fission.
• Binary fission: The circular DNA replicates and so do the plasmids. The cell membrane begins to grow and the cytoplasm divides. A new cell wall forms dividing the cells into two identical daughter cells
• As viruses are non-living they cannot undergo cell division. They replicate by attaching to their host cell with the attachment proteins on their surface.
• Viruses inject their nucleic acid into the host cell. The genetic information on the injected viral nucleic acid provides “instructions” for the host cells metabolic processes to produce viral components
• The viral components produced by a host cell consist of nucleic acid, enzymes and structural proteins. Creating new viruses
• Cytokinesis failure can indicate a tumour
• Without cytokinesis the cells cytoplasm does not divide, forming a multinucleated cell