Mitosis Meiosis

• What is the main focus of the BIS4016 Cell Biology course?

  Mitosis and meiosis processes
• What are the learning objectives of the course?

  Understand M phase processes and differences
• What phases comprise the interphase of the cell cycle?

  • G1 phase: Preparation for DNA replication
  • S phase: DNA replication occurs
  • G2 phase: Growth phase for mitosis
• What regulates the cell cycle?

  Restriction points and checkpoints
• What happens during the G0 phase?

  Cells enter cell cycle arrest
• What follows interphase in the cell cycle?

  M phase
• What does M phase consist of?

  • Mitosis
  • Cytokinesis
• What occurs during prophase of mitosis?

  • Chromosomes condense
  • Nucleolus disassembles
  • Microtubules form centrosomes
• What is the role of mitotic spindles during prophase?

  They prepare for chromosome division
• What happens during prometaphase?

  • Nuclear envelope disappears
  • Chromosomes attach to microtubules
  • Kinetochores form
• What is the spindle assembly checkpoint?

  Checks chromosome and spindle alignment
• What occurs during the disassembly of the nuclear envelope in prometaphase?

  • Membrane bilayers removed
  • Nuclear pores disassembled
  • Nuclear lamina dispersed
• What are the three classes of microtubules in the mitotic spindle?

  Kinetochore, astral, and interpolar microtubules
• What is the function of kinetochore microtubules?

  • Pull chromatids apart
  • Attach to spindle poles
• What happens during metaphase?

  Chromosomes align at the metaphase plate
• What is the role of cyclin B and securin during metaphase?

  They are destroyed for chromatid separation
• What characterizes anaphase?

  • Sister chromatids are pulled apart
  • Anaphase A and B events occur
• What activates the cell cortex in preparation for cytokinesis?

  Mitotic spindles
• What are the three factors regulating sister chromatid separation?

  • Cohesin
  • Separase
  • Securin
• What happens to securin after the last chromosome aligns correctly?

  Securin is degraded
• What occurs during telophase?

  • Contractile ring assembles
  • Cytokinesis occurs
• What promotes nuclear envelope assembly?

  • Ran-GTP
  • ELYS scaffold protein
• What guides the separation of daughter cells during cytokinesis?

  Actin filaments and Myosin-II
• What is meiosis?

  • Process for producing gametes
  • Maintains chromosome numbers
  • Generates genetic combinations
• What type of cells undergo meiosis?

  Eukaryotic cells
• What are diploid cells?

  • Cells with two copies of each chromosome
  • One from each parent
• What happens to chromosome numbers during meiosis?

  They are halved to form haploid gametes
• What are the three essential events in preparing for meiosis?

  1. Pairing of homologous chromosomes
  2. Homologous recombination
  3. Segregation of chromosomes
• What are the two parts of meiosis?

  • Meiosis I: Reductional division
  • Meiosis II: Equational division
• What occurs during anaphase I of meiosis?

  Homologous chromosomes are pulled apart
• What happens during prophase II of meiosis?

  • Chromosomes condense
  • Nuclear envelope dissolves
• What is the consequence of chromosomes failing to segregate during meiosis?

  Daughter cells lack normal haploid numbers
• What is polyploidy?

  • Gain of an entire set of chromosomes
  • 1-3% of conceptions are triploid
• What is aneuploidy?

  • Loss or gain of chromosomes
  • Most zygotes die during development
• What are the key differences between mitosis and meiosis?

  • Mitosis: One division, diploid products
  • Meiosis: Two divisions, haploid products
  • Meiosis: Genetically different products
• How does prophase I of meiosis differ from prophase of mitosis?

  • Prophase I is longer
  • Involves pairing and recombination
• What is the recombination rate in meiosis compared to mitosis?

  • 100-1000 fold higher in meiosis
• Where can further reading on this topic be found?

  Chapters 44 and 45 of Cell Biology