Week 8 - Segregating Chromosomes

BIOL230W Week 8 – Segregating Chromosomes We have spent the first half of the semester focused on the flow of information from DNAà RNAà protein using cystic fibrosis as a model. Now we will spend a few weeks looking at the roles proteins play in the cell including signaling, cell division and cell cycle regulation. These processes are important to cell function and when they fail can result in the development of cancer. Day 1 Learning Objectives 1. Compare and contrast centromere, chromosome, chromatid and kinetochore with respect to structure, function, location, stage and phase. 2. Compare and contrast the amount and location of DNA at each stage of the cell cycle 3. Describe the main processes occurring in each of the four stages of the cell cycle 4. Outline the structures and result of each phase of mitosis Mini-Lecture: Intro to Cell Cycle and Cancer Small Group Activity: Previous Knowledge Activate! Form a scaffold to which new knowledge can be attached. 1. What are the 4 stages of the cell cycle? 61 , 62 M-phase , and S-phase , 2. Which stages are included in interphase? Gl , G2 , and S-phase 3. What happens in S-phase? Duplication of DNA and cellular contents 4. In which stages would you find sister chromatids? S , 62 , and M ⑨88 5. What macromolecule makes up the centromere? DNA (heterochromatic) and proteins (histones Mini-Lecture: DNA in Interphase 6. Is G0 a part of interphase? Go is not in the cell cycle 7. Compared to G1, how much DNA is in the nucleus of a cell in G2? Double the DNA content Ex : Gl In = 10 62 In = 20 8. What is the function of cohesin? To attach the sister chromatids to each other Attaches sister chromatids Small group activity: DNA in Interphase 9. Using the images below indicate which stages are interphase or mitosis. 10. Given the provided cellular membranes below, draw two individual chromosomes in G1, S and G2 ONLY. Indicate the presence of euchromatin vs heterochromatin, sister chromatids, cohesion, the centromere and the nuclear membrane. 1 BIOL230W Week 8 – Segregating Chromosomes euchromatic chromosome sinSee & .. m & - ↑ % · Mini Lecture: DNA In Mitosis 11. What is the purpose or result of mitosis? To replicate DNA into 2 separate daughter · cells (loosecondensed 12. Compared to G2, how is the structure of chromosomes different in mitosis? In 62 , chromosomes In M , are chromosomes are duplicated , euchromatic duplicated, heterochromatic 13. Based on chromatin structure in interphase vs. mitosis, how would you expect the overall level of gene expression to differ? Reduction of gene expression once chromosomes condense 14. Compared to G2, how much DNA is in the cell in prophase? The same amount 15. Compared to metaphase, how much DNA is in the cell in anaphase? The same amount Small Group Activity: DNA in Mitosis Go back to the cell drawing for DNA structure in interphase. NOW, use what you have learned in class today and previous knowledge to draw your interpretation of the structure of DNA in the phases of mitosis. Be sure to include the two chromosomes, sister chromatids, cohesin, the nuclear membrane and the centromere. Make sure your drawing reflects the heterochoromatic nature of the chromosomes. 2 BIOL230W Week 8 – Segregating Chromosomes Day 2 Learning Objectives 1. Compare and contrast the polymerization of microtubules with the polymerization of DNA/RNA and proteins 2. Describe how the structure of microtubules contributes to its function in interphase and in mitosis. 3. Apply the concept of “dynamic instability” to the structure and function of microtubules in mitosis. 4. Compare and contrast the 3 different types microtubules that create the mitotic spindle with respect to attachment and function. 5. Draw and label the different stages of mitosis (with respect to the DNA structure, microtubule structure, kinetochore, nuclear membrane and centrosome and cohesin) Mini-Lecture: How does the DNA Move? Microtubules and Kinetochores GTP 16. Tubulin monomers polymerize when they are bound to __________ and depolymerize when they GD are bound to ______________. 17. How might the lack of GTP affect the stability of a microtubule? subunits can not bind to GTP to add to growing plus end , it results in Catastrophe (spontaneous depolymerization 18. Given your answer to Q16, in what category of protein might you place the tubulin monomer? G-protein 19. Take a few minutes to compare and contrast the microtubule polymer with two other polymers (DNA/RNA and proteins) we have studied. Use Q. 20 and 21 to record your answers. DNA/RNA Monomers Polarity Connecting bond Polymerizing Agent Protein Microtubules Nucleotides Amino acids Tubulin dimers 3'/5' N/C plus/minus end end terminus Phosphodiester peptide DNA/RNA polymerase ribosome bond hydrogen bonds nothing 20. How is the polymerization of microtubules similar to the polymerization of nucleic acids and proteins? It is dependent on the presence of a certain molecule (GTP 21. How is the polymerization of microtubules different from the polymerization of nucleic acids and proteins? There is no agent required as it will self-polymerize 22. What function of microtubules is dependent on the bond that joins microtubule monomers into a polymer as described in Q21? (hint – microtubules are not permanent structures)? Their ability to rapidly switch between growth and shrinkage 23. What organelle nucleates microtubule polymers? Centrosome 3 BIOL230W Week 8 – Segregating Chromosomes Small Group Activity: Microtubules During Interphase Go back to the cell drawing for DNA structure in interphase. Use what you have learned in class today to draw your interpretation of the location of microtubules in interphase. Be sure to include the microtubules, the centrosome(s) and nuclear membrane. Mini-Lecture: Spindle formation and chromosome attachment 24. What cellular event allows microtubules to invade the nuclear space during prometaphase? The nuclear membrane disintegrates 25. What type of macromolecule is a kinetochore? Protein 26. Centromeres and kinetochores are present during which phases of the cell cycle (G1, S, G2, M)? Centromere = 61 62 5 M Kinetochore M , , , 27. What does the + end of each of the three types of mitotic microtubules attach to? One type connects extends to wards to the centrosome membrane on the (stabalize Spindle) , another attaches to a microtubule coming from another pole , and another Kinetochore 28. How does the dynamic instability of the microtubule relate to the attachment of microtubules to chromosomes? to Kinetochores It allows microtubules to efficiently search for and attach 29. What provides the force to position the chromosomes at the center of the cell at metaphase? Kinesin walking along the microtubule and pulls it to the pole Small Group Activity: Microtubules During Mitosis Go back to the cell cycle drawing. Use what you have learned in class today to draw your interpretation of the location of microtubules in mitosis. Be sure to include the microtubules (Polar, kinetochore and Astral), the centrosome(s), kinetochore and nuclear membrane. At Home Practice: Here are some extra cell outlines. See if you can remember all the structures and locations in the different stages of the cell cycle without looking! Try using different colors to highlight the various structures. 4 BIOL230W Week 8 – Segregating Chromosomes 5