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Professor: Hufford/Biederman S.I. Leader: Stephanie Schneider Biology 211 (2) Week 9! ! Chapter 12! VOCABULARY: ! Anaphase: A stage in mitosis Cell division: Creation of new cells by division of or meiosis during which chromosomes are moved to preexisting cells opposite poles of the spindle apparatus Centromere: joint point where the two sister chromatids meet Chromatid: One of the two identical double-stranded DNAs composing a replicated chromosome that is connected at the centromere to the other strand. Chromosomes: Genecarrying structure consisting of a single long molecule of double-stranded DNA and associated proteins. Cyclin: One of several regulatory proteins whose concentration fluctuate cyclically throughout the cell cycle. Involved in the control of the cell cycle via cyclin-dependent kinases Cyclin-dependent kinase (Cdk): Any of several related protein kinases that are functional only when bound to a cyclin and are activated by other modifications. Involved in the control of the cell cycle Cytokinesis: Division of the cytoplasm to form two daughter cells. Typically occurs immediately after division of the nucleus by mitosis or meiosis G1 phase: The phase of the cell cycle that constitutes the first part of interphase before DNA synthesis G2 phase: The phase of the cell cycle between synthesis of DNA (S phase) and mitosis (M phase); the last part of interphase Gametes: A haploid reproductive cell that can fuse with another haploid cell to form a zygote. (EX: sperm and egg) Kinetochores: A protein complex at the centromere where microtubules attach to the chromosome. Meiosis: In sexually reproducing organisms, a special two-stage type of cell division in which one diploid parent cell produces haploid gametes, results in having of the chromosome number Metaphase: A stage in mitosis or meiosis during which chromosomes line up in the middle of the cell Mitosis: The process of nuclear division that results in two daughter nuclei genetically identical with the parent nucleus MPF: (M-phase-promoting factor) A complex of a cyclin and cyclin-dependent kinase that, when activated, phosphorylates a number of specific proteins needed to initiate mitosis p53: A tumor-suppressor protein that responds to DNA damage by stopping the cell cycle, turing on DNA repair machinery, and may trigger apoptosis Prometaphase: A stage in mitosis or meiosis during which the nuclear envelope breaks down and microtubules attach to kinetochores Professor: Hufford/Biederman S.I. Leader: Stephanie Schneider Prophase: The first stage in mitosis or meiosis during which chromosomes become visible and the spindle apparatus forms S phase: They phase of the cell cycle during which DNA is synthesized and chromosomes are replicated Sister chromatids: The paired strands of a recently replicated chromosome, which are connected at the centromere and eventually separate during anaphase of mitosis and meiosis II. Interphase: non-dividing phase Spindle apparatus: The array of microtubules responsible for moving chromosomes during mitosis and meiosis; includes kinetochore microtubules, polar microtubules and astral microtubules Telophase: The final stage in mitosis or meiosis during which daughter chromosomes have separated and new nuclear envelopes begin to form around each set of chromosomes Tumor suppressors: A protein (e.g. p53 or Rb) that prevents cell division, such as when the cell has DNA damage. Mutant genes that code for tumor suppressors are associated with cancer. KEY CONCEPTS:! 1. Why does replication occurs in an uncondensed state?! 1. It is easier for the polymerase to copy the DNA when it is unraveled rather than raveled. ! 2. Diagram the cell cycle, labeling the G1, G2, S and M phases. Draw the chromosomes present at each stage. How much DNA is in the cell at G2 compared to G1? How much DNA is in each daughter cell compared to the parent cell? ! Professor: Hufford/Biederman S.I. Leader: Stephanie Schneider 3. Chromosome replication occurs only during _______.! 1. S Phase in the Interphase, there is no chromosome replication occurring during M Phase! 4. Diagram the sub-phases of mitosis. Label and describe each phase.! 5. What three structures make up the the mitotic spindle? Define each.! 1. Spindle fibers: what the microtubules are made of! 2. Polar microtubules: push the poles of the cell away from each other during mitosis! 3. Kinetochore microtubules: pull chromosomes to the poles of the cell during mitosis! 6. Diagram the concentrations of cyclin and MPF-Cdk during the cell cycle. How does MPF trigger the start of mitosis?! 1. One phosphorylation on Cdk =active <— triggers the start of mitosis! ! 2. Two phosphorylation on Cdk=inactive <—have two until M Phase begins! Professor: Hufford/Biederman S.I. Leader: Stephanie Schneider 7. Compare and contrast G1, G2 and M checkpoints. Why is it important for the cell cycle to have checkpoints? What would happen to a cell that has a damaged p53 gene so that it cannot make functional p53 protein?! 1. It is important because cells that fail a checkpoint are marked with a p53 gene and labeled for cell death. If a cell has a damaged p53 gene, the cell may pass a checkpoint, even if they have failed it. This will lead to uncontrolled growth (i.e. cancer).