NE102 Lecture Notes 2

S phase dna duplication chromosomes are attached g2

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Unformatted text preview: S phase DNA duplication Chromosomes are attached G2 phase Cell makes sure that everything that has happened so far is correct G2 checkpoints Is all DNA replicated? Cell Division Guest Lecture: Lucia Pastorino 19:00 Is all DNA damage repaired? M Mitosis and cytokinesis Mitosis checkpoints Are all chromosomes properly attached to the mitotic spindle? CYCLINS AND CYCLIN-DEPENDENT KINASES Cyclins and cyclin dependent kinases to regulate the progression of the cell cycle Cyclin activates CDK so that CDK can accept a phosphate group Specific binding between cyclin and cyclin-dependent kinas (CdK) S-Cyclins Help cell go through G1-G2 phases Levels drop when M phase begins M-Cyclins Help cells go through M phase Levels low until cell enters M phase Deactivation of specific Cdks occurs by degradation of the partner cyclin Ubiquitinate the cyclin to degrade the cyclin-Cdk complex DNA damage: checkpoint in G2 phase to stop progression of the cell cycle X-rays causes DNA damage Activates protein kinases that phosphorylate p53, stabilizing and activating it. Cell Division Guest Lecture: Lucia Pastorino 19:00 MITOSIS During mitosis, chromosomes segregate into two newly formed cells, moving on the mitotic spindle The chromosomes are pulled to the extremities of the spindles: a mechanism necessary to allow cell division What generates the mitotic spindle? When does it form? Centrosomes duplicate during interphase and form the two poles of the mitotic spindle Mitotic spindle is formed when the polar microtubules organize and stabilize interacting with one another Tubules of the mitotic spindle attach to the kinetochores around the centromere region of the chromosomes. Different phases Prophase When the centrosomes separate and give origin to the mitotic spindle Prometaphase When the nuclear membrane breaks and chromosomes attach to the spindle Metaphase: when the chromosomes align on the spindle Anaphase: when the sister chromatids separate and chromosomes segregate Anaphase A: chromosomes are pulled pole-ward Anaphase B: poles are pushed and pulled apart Anaphase Promoting Complex (APC): destruction of cohesins – proteins that bind sister chromatids together Telophase: when the chromosomes arrive at the poles of the spindle and a contractile ring is formed. Cytokinesis: when the newly formed cells divide Cell Division Guest Lecture: Lucia Pastorino 19:00 WHAT IF CELLS THAT ARE NOT SUPPOSED OT DIVIDE RE-ENTER THE CELL CYCLE? Neurons are post-mitotic 1 study: Cdk5 activity is increased in Alzheimer-diseased brains The cell cycle in cells and mature neurons? Can enter the cell cycle but will not complete Won’t undergo mitosis Called neuronal aberrant cell cycle re-entry A permissive event to neurons vulnerability...
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S phase DNA duplication Chromosomes are attached G2 phase...

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