BICD 110 F24 Lecture 9A preview

BICD 110: Cell Biology

  • Instructor: Dr. Amy Kiger

  • Lecture Date: November 26, 2024

Quiz Details

  • Quiz 2 results handed back after class.

  • Unclaimed graded quizzes available at Biology Exam Depot (email to schedule).

  • Canvas will not show combined scores (Exam & Extra Credit separate).

  • Regrade requests accepted until December 6th (must include original test).

Announcements

  • No sections this week; next sections meet Week 10.

  • Upcoming assignments:

    • Canvas Questions (Week 9) due Monday at 11:59 PM.

    • Problem Set 9 due Tuesday at 11:59 PM.

    • Extra Credit due Thursday at noon (extended deadline).

  • Office hours for Week 9:

    • Nov 25: Dr. Kiger (Hybrid) 11:00 AM - 1:00 PM.

    • Nov 26: Jibin Zhang (Zoom) 9:30 - 10:30 PM.

    • Nov 26: Daniel Gurholt (Hybrid) 5:00 - 6:20 PM.

    • Nov 27: Ethan Lee (Zoom) 2:00 - 3:00 PM.

    • Nov 27: Billy Santoso (Zoom) 4:00 - 5:00 PM.

Today’s Agenda

  • Review of motor protein assays.

  • Mitosis review.

  • Overview of cell cycle, including methods, oscillations of Cdks/cyclins, and checkpoints.

Assays for Motor Motility

  1. Bead Assay:

    • Uses fluorescent beads coated with motors + ATP.

    • Follow motility on a slide with microtubules.

    • If motor isn’t processive, the bead may fall off quickly.

  2. Gliding Assay:

    • Fluorescent polymers + ATP tracked on motor protein-coated surfaces.

    • Challenges in single molecule assays, but easier to measure.

  3. In vivo Assay:

    • Track labeled cargo using microscopy; squid giant axon useful for visualization.

Cell Cycle Overview

  • Ordered events leading to division:

    • Mitotic Cycle: 1 cycle, 2 identical daughter cells.

    • Meiotic Cycle: 2 cycles, results in 4 non-identical daughter cells.

    • Meiosis I: Reduction to half DNA content.

    • Meiosis II: Segregation of sister chromatids.

Phases of the Cell Cycle

  • Interphase:

    • G1 phase (growth), S phase (DNA replication), G2 phase (preparing for mitosis).

  • M Phase (Mitosis): Chromosome segregation and cell cleavage.

Mitosis Stages

  • Key structures: Chromosomes, Sister chromatids, Centromere, Kinetochore, Mitotic spindle.

  • Stages:

    • Prophase

    • Prometaphase

    • Metaphase

    • Anaphase

    • Telophase

    • Cytokinesis

Cell Cycle Regulation

  • Cdk Activity: Cycles of activity determine transitions; specific combinations for different stages.

  • Checkpoints: Ensure errors are corrected before proceeding to the next phase.

  • Main checkpoints: G1/S transition, G2/M transition, Metaphase/Anaphase transition.

Key Concepts in Cell Cycle Study

  • Use of model organisms: budding yeast, fission yeast, frog oocytes, fruit flies, human cancer cell lines.

  • Cyclin-dependent kinases (CDKs) regulate cycle transitions and activity oscillates throughout cell cycle.

Advances in Understanding Cell Cycle

  • Discovery of Cyclins through experiments in sea urchin embryos and frog egg extracts.

  • Cyclins are essential triggers for M-phase entry, with dependencies on RNA synthesis.

Conclusion

  • Proper sequencing of cell cycle stages ensures fidelity in cell division and growth.