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The role of the Cell Cycle in an Organism - Coggle Diagram
The role of the Cell Cycle in an Organism
Mitosis
Prophase: The DNA chromatin condenses into chromosomes, centrioles form and go to the two poles of the cell
Metaphase: Spindle fibers form from the centrioles, and attach to the centromeres of the chromosomes. They align them along the middle of the cell.
Anaphase: The spindle fibers retract and separate each of the chromosomes into 2 sister chromatids.
Telophase: Nuclear membranes form around the two sets of chromatids, which decondense. After this, the cytoplasm splits and two daughter cells are created (cytokinesis).
Chromatin = unraveled DNA
Chromosomes = condensed chromatin, takes on iconic "X" shape
Centromeres = circular structure at the middle of chromosomes which spindle fibers attach to (they actually attach to the kinetchores, proteins inside the centromeres
Centrioles = always come in pairs, are the site where the spindle fibers start to grow.
Spindle Fibers = long microtubes that sprout from the centrioles and attach to the chromosomes in order to divide them.
Mitotic inhibitors are factors that inhibit/interfere with mitosis. The spindle fibers are most affected by mitotic inhibitors
Binary fission = when a single-celled organism divides into two.
Cell Cycle
G1 phase = cell grows and develops organelles. Duration: 11 hrs
G1 checkpoint = p53 protein checks to see if the cell + its organelles have grown properly and there is no damage to its DNA.
S phase = the cell's DNA is replicate fully. Duration = 8 hrs
G2 phase = cell grows further, cell creates proteins needed for proteins. Duration = 4 hrs.
G2 checkpoint = checks for proper cell growth, damage to DNA, and if proteins needed for mitosis are made.
M (Mitosis) phase = cell divides into 2 daughter cells. Metaphase checkpoint checks if the spindle fibers are attached to the chromosomes. Duration = 1 hr
Apoptosis = programmed cell death; Faulty cells have chemical markers attached to them that are recognized by killer cells. These cells destroy the faulty cell, but have its contents recycled.
CDKs and cyclins are enzymes and the proteins that bind to CDK respectively. Cyclins activate CDKs by binding to them, and they transfer a phosphate group to a target protein. This target protein goes on to cause some event (i.e. more cell growth) in the cell cycle. After they serve their purpose, te cyclin detaches and breaks down, and the CDK becomes inactive.
DNA replication is semi-conservative as there ends up being one original strand and one newly created strand. This method is less likely to have errors in copying DNA .
p53 = protein that checks if the cell is working and built properly (no abnormalities in organelles, protein production, etc.). It usually does this at the G1 stage checkpoint.
G0 phase = when the cell fails the G1 checkpoint, or is a cell type that doesn't have to grow or divide (i.e. nerve cells), it stays in the G0 phase.
CELLS CANNOT MOVE THROUGH THE STAGES OF THE CELL CYCLE WITHOUT THE PROPER SIGNALS
Cells spend most of their lives in interphase (G1, S, G2)
Cancer and Genes
Cancer = a disease of the cell cycle caused by uncontrollable growth and division of cells, which end up forming tumors. Only ONE of the oncogenes in a pair has to be mutated to cause cancer (dominant).
Oncogenes = genes that promote cell division and growth
Tumor Suppresor Genes = genes that control/limit cell growth and division --> TWO tumor suppresor genes out of a pair must be mutated to cause cancer (recessive).
Mutated oncogenes promote too much cell growth and thus division, while mutated tumor suppressor genes result in no limit to cell growth and division (Like pushing the accelerator too much or taking away the brakes of a car respectively).