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21 Cards in this Set
- Front
- Back
Cell Cycle: M Phase Events |
•Nuclear division occurs in four stages (prophase, anaphase, metaphase and telophase). •This is followed by cytokinesis - division of the cytoplasm. |
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Cell Cycle: M Phase Checkpoints |
•A checkpoint chemical triggers the condensation of chromatin. •The metaphase checkpoint ensures that the cell is ready to complete mitosis. |
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Cell Cycle: G1 Phase Events |
•Cells grow and increase in volume. •Protein synthesis occurs to produce enzymes needed for S Phase. •Organelles are replicated. |
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Cell Cycle: G1 Phase Checkpoints |
•A G1 checkpoint control mechanism ensures that the chemicals needed for DNA replication are present and that the DNA is undamaged before entering the S-phase. •The p53 gene also helps to control the G1 Phase. |
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Cell Cycle: S-phase Events |
•DNA is replicated. |
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Cell Cycle: S-phase Checkpoints |
•Once the cell enters the S-phase it is committed to completing the cell cycle. •Genes active in all cell types are copies first. •Genes usually inactive in specific cell types are copied last. |
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Cell Cycle: G2 Phase Events |
•Cells continue to increase in volume. |
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Cell Cycle: G2 Phase Checkpoints |
•The G2/M checkpoint ensures that the DNA has been replicated without errors before entering mitosis. •Chemicals ensure the cell is ready to start mitosis by stimulating proteins that will be involved in chromosome condensation and spindle formation |
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Mitosis and Meiosis Differences |
Mitosis: •Necessary for growth and repair of tissues. •1 division •2 daughter cells formed. •Results in genetically identical cells. •Number of chromosomes stays the same. •Produces diploid cells. •Asexual reproduction. Meiosis: •Takes place in the reproductive organs to produce gametes. •2 divisions •4 daughter cells formed. •Results in genetically different cells. •Number of chromosomes is halved. •Produces haploid cells. •Sexual reproduction. |
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Haploid |
Haploid - A cell or organims that has one copy of each chromosome. |
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Diploid |
Diploid - cells or organisms that have two copies of each chromosome in their nuclei. |
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Mitosis - Definition |
Mitosis is the process by which new body cells are produced for: •Growth •Replacing damaged or old cells and reparing tissues. |
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Homologous Chromosomes |
Most cells of the body contain chromosomes in matching pairs that hold the same genes at the same positions along the chromosome. These pairs are called homologous chromosomes. |
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Histone |
A protein that DNA is wrapped around to form chromatin. |
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Chromatids |
The "arms" of a replicated chromosome. |
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Centromere |
The area of a chromosome where two sister chromatids are joined together. |
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Mitosis: Prophase |
•Chromosomes shorten and thicken by supercoiling to form sister chromatids. The chromosomes are now visible. •The nuclear envelope breaks down. •The centriole divides in two and the two centrioles move to opposite poles of the cell. •Spindle fibres are formed between the two centrioles from a cytoskeleton protein called tubulin. |
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Mitosis: Metaphase |
•Chromosomes move to the equator of the cell. •Chromosomes attach to the spindle by their centromeres. |
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Mitosis: Anaphase |
•Centromere splits. •The spindle shortens, pulling sister chromatids in opposite directions towards the poles of the cell. |
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Mitosis: Telophase |
•Chromatids reach the poles of the cell. •New nuclear envelope forms around each set. •Spindle breaks down. •Chromosomes uncoil and become invisible again. |
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Cytokinesis |
•Occurs after mitosis. •The cytoplasm and organelles are divided into two and the cell splits to form two daughter cells. |