Cell Cycle and Mitosis

Objectives:

• Know the parts of the cell cycle: Interphase, M phase, Cytokinesis

• Understand mechanisms of cell division: reproduction, growth, repair, or replacement of cells

• Know the cell cycle processes of Interphase at G₁, G₂, G₀, and S phases 

• Identify the names of the phases of mitosis and the characteristics of each phase 

• Know the types of chromosomes present in each phase of the cell cycle

  ---

  General terms:

  • Chromosomes: condensed DNA (DNA + protein ) 

    • pre interphase: 46 chromosomes (single chromatids)

    • Post interphase: 46 chromosomes (replicated chromatids attached)

    • 2N = 4 → two sets of chromosomes, total number chromosome is 4

  • Centromere:

    • hold together sister chromatids

  • Centriole:

    • organelles involved in the creation of spindle fibers

  • Spindle Fibers:

    • protein structure aiding division

  Cell cycle:

• interphase:

  • the cell grows, makes copies of its DNA

  • the longest phase of the cell cycle

  • preparation for division occurs in 3 steps:

    • G1 phase: cell grows physically larger, copies organelles, and makes molecular building steps *checkpoint, check if cell is large enough

    • S phase: cell synthesizes a complete copy of DNA in its nucleus and duplicates centrisomes

    • G2 phase: cell grows more, makes proteins and organelles, begins to reorganize in preparation of mitosis *checkpoint, successful DNA replication (no errors)

  • chromatin

• Mitosis: cell divides its copied DNA and cytoplasm to make 2 new cells

  • purpose: assexual repreduction, make cells, replace cells

    • prophase: chromatin condenses into replicated chromosomes, spindle fibers (made of tubulin, move chromatids) begin to assemble from the centrioles, nuclear envelope begins to break down (longest phase of mitosis)

      • replicated chromosomes

    • prometaphase: the nuclear membrane is completely broken down and spindle fibers (already attached to the k___ on centrioles) attach to the replicated chromosomes.

      • replicated chromosomes

    • metaphase: the genetic material in the nucleus becomes aligned along the equatorial plane of the cell (middle). The chromosomes are attached to spindle fibers. *checkpoint, ensure spindle fibers attached 

      • replicated chromosomes

    • anaphase: the replicated chromosomes are separated —> two identical daughter chromatids. The sister chromatids are pulled apart by the spindle fibers (GTP necessary to separate the chromatids)

      • sister chromatids

    • telophase: condensed chromosomes begin to decondense, cell is cleaved into two new daughter cells and daughter nuclei form at each pole. A new nuclear envelope begins to form around each set of separated chromatids.  

      • chromatids and then chromatin (towards end when cytokinesis begins)

• Cytokinesis: final stage of the cell cycle

  • cytoplasms of the two cells split to form two identical cells

  • the sister chromatids are now chromatin and the two cells will return to interphase

  

• Cytokinesis plant v. animal:

  • Plant division starts at the center of the cell and moves towards the cell wall

  • Animal division starts at the edges of the cell at the plasma membrane and moves towards the center

  • plants create Create vesicles that fuse → cell plate

• Mitosis vs. Binary fission:

  • binary fission is type of cell division (mostly in prokaryotes and bacteria)

    

• Cancer and Cell cycle: