SCB 201 lab 5/6/20. Announcements SCB 201 lab 5/6/20. Announcements Quiz 2 is available now through Friday (note the extension due to photosynthesis notes disappearing…they are back now). Quiz 1 is...

i need help with my hw assignment



SCB 201 lab 5/6/20. Announcements SCB 201 lab 5/6/20. Announcements Quiz 2 is available now through Friday (note the extension due to photosynthesis notes disappearing…they are back now). Quiz 1 is graded (or will be by today). Signature assignment rough draft due this Saturday (5PM) by email (about cellular respiration…see assignment instructions on blackboard for details). Remaining grades: HW related to several more labs. Signature assignment final draft due (on ePortfolio) by June 8th. Quiz 3 will be posted on May 27th Quiz 4 will be posted on June 10th (during finals week). There is no microscope element included in quiz 4. Review: Types of Nuclear Division (Mitosis & Meiosis) Two different types of nuclear division are seen in eukaryotic cell division: mitosis & meiosis. The usual type of cell division is mitosis which produces cells for growth & repair. Meiosis produces cells with half the chromosomes of the parent cell. These cells are typically gametes (sex cells). Note: The questions you should answer and turn in by next week are in RED on the last few slides. Mitosis: the 2 daughter cells are genetically identical to the parent cell Fig. 8.7 Meiosis: the 4 daughter cells have half the number of chromosomes of the parent cell Cell Cycle (Interphase & Mitotic Phase) Cell Cycle – sequence of stages a eukaryotic cell goes through from the time it is created (by division of a parent cell) to the moment it undergoes mitosis. Interphase – the part of the Cell Cycle in which a cell is not dividing. Includes G1, S & G2 phases. Mitotic phase (M phase) – the part of the Cell Cycle when a cell is dividing by mitosis. The Cell Cycle Fig. 8.5 Interphase G1 (Gap 1) phase: growth & metabolism. About 7-9 hrs S phase: DNA synthesis & chromosome replication. About 6-8 hrs G2 (Gap 2) phase: preparation for cell division (includes formation of new organelles, etc…) About 4-5 hrs Mitotic phase Cell division. About 30-45 mins Total cell cycle: About 18-24 hrs. Cells which have stopped dividing exit the cell cycle permanently or until a signal to divide again is received and are referred to as being in “G0” Stages of Mitosis & Cytokinesis Mitosis is divided usually into 4 stages: Prophase: chromosomes condense, spindle forms, nucleolus disappears, nuclear membrane breaks down Metaphase: chromosomes move to equator & align at metaphase plate Anaphase: chromatids separate into daughter chromosomes & move to opposite poles Telophase: nuclear envelopes reform around daughter chromosomes, which unwind https://www.youtube.com/watch?v=N97cgUqV0Cg Stages of Meiosis Unique to meiosis: Tetrads/crossing over during Prophase I (doesn’t occur in mitosis). Generates genetic diversity. Tetrads line up in the middle of the cell during Metaphase I. This doesn’t happen in Mitosis (homologs line up next to each other). Two rounds of cell division Sister chromatids not separated until anaphase II 4 non-identical haploid cells are produced. Experimental considerations related to cell division. Cell division is an intensely studied topic due to the direct relevance to cancer, development, and other issues. What sort of topics are studied? Examples include the effect of environmental pollution on mitosis, attempts to develop anti-cancer drugs, the basis of developmental issues in people, etc… Hypothetical experiment: Effect of heavy metal poisoning on mitosis. The presence of high levels of “heavy” metals such as lead, mercury, copper, cadmium, etc. in the environment can represent a hazard to human health (think of lead paint). Imagine that you want to investigate the potential effects of heavy metal exposure on mitosis. What might be a good hypothesis in this regard? Remember a good hypothesis should be specific, testable, and make predictions. A good hypothesis might be “High levels of copper will inhibit mitosis resulting in decreased rates of new cell production in cultured cells.” A bad hypothesis might be “Copper causes changes to mitosis.” Imagine that you tested the hypothesis we mentioned above (the good one). Consider the results on the following slide: Results: Here we see hypothetical cell density results for our experiment. We have initial amounts of cells per microliter (note that they are the same for both conditions) and then we see cells present per microliter after two days. Assignment: Do the results support or fail to support the hypothesis? Explain. What is the dependent variable here? What is the independent variable? Might there be other possible explanations for these results? If so, what? High copper environmentNormal copper environment Cells present at time zero1000/uL1000/uL Cells present at 48 hours1200/uL3000/uL Exercise: Microtubule stabilizing agents. Think back to mitosis. How are chromatids actually pulled apart and moved during anaphase? Be specific. What do the microtubules actually do that makes the chromatids move? A variety of molecules have been shown to prevent microtubule depolymerization. How would this effect mitosis? Explain. Why might such molecules be used to treat cancer? Please look up one microtubule stabilizer (other than Taxol/paclitaxel) that has been used or considered as a cancer treatment. Include a link to your source. Hypothesis: Microtubule stabilizing agents cause dividing cells to arrest in anaphase. Results Cells counted in each stage after 24 hours:Control cells (no treatment)Treated with Mictrotubule stabilizing agent Prophase10312 Metaphase101375 Anaphase10410 Telophase10011 Note: Both control and treated conditions contained the same number of cells synchronized in G1 at the beginning of the experiment. Interpretation: Do the results presented on the prior slide support or fail to support the hypothesis? Explain. If the hypothesis is supported, please explain why that makes sense. If the hypothesis is NOT supported, please explain why that makes sense. (roughly one paragraph).