The Life Cycle of the Cell and Mitosis Sections 8.1, 8.2, 8.6, 8.7, 8.8

The Life Cycle of the Cell

G1 Stage G1 = Growth or Gap Cell Increases in Size Cell Performs its role, job or function

S Phase S = Synthesis Cell Replicates [copies] its DNA Cell continues to perform its job

G2 Stage Cell continues to perform its job Cell prepares all other material necessary for the Mitosis [Cell Division]

Interphase G1 + S + G2 = Interphase Phase / Stage between Divisions Not Technically part of Mitosis but included in discussion PLANT OR ANIMAL

INTERPHASE

Mitosis Definition: Cell Division Producing Two Genetically Identical Daughter Cells Two Major Events Karyokinesis: Division of the Nucleus Cytokinesis: Division of the rest of the Cell Divided into Four Stages Divisions made on morphology [physical appearance] and cellular activity [what the cell is doing]

Prophase Observable Events: DNA condenses from Chromatin to Chromosome form. The Nucleolus “Disappears”. The Nuclear Envelope “Disappears” Mitotic Spindle Apparatus Forms Prophase Congression occurs Animal Cells Only: Centrioles Migrate to opposite ends of cell

Prophase [continued] Chromatin v. Chromosome DNA Long, Thin, Useable v. Short, Thick and Inaccessible Nucleolus “Disappears” as DNA condenses Nuclear Envelope Stored in Rough E.R. Mitotic Spindles: Protein Strands [microtubules] used to separate chromosomes; attach to the Centromere Prophase Congression: Movement of the Chromosomes to Plane of Division

Prophase [continued]

PROPHASE

Metaphase Observable Event: Centromere of the Chromosomes line up at the Plane of Division [usually the middle of the Cell]

Metaphase [continued] Centromere: Part of the Double Chromosome to which the Mitotic Spindles Attach Chromatid: one half of a Doubled Chromosome NOT used when Chromosome is Single [prior to the S Phase or After Anaphase]

METAPHASE

Anaphase Observable Event Double Chromosomes Split into Single Chromosomes Caused by Mitotic Spindles Pulling Apart the Chromatids Single Chromosomes move [pulled] to opposite ends of the cell.

ANAPHASE

Telophase Observable Events: “Reverse of Prophase” DNA Decondenses from Chromosome form to Chromatin form Nucleolus “Reappears” Nuclear Membrane “Reappears” Mitotic Spindles Disassemble

Telophase [continued] Observable Events [continued] Cytokinesis: Division of the rest of the cell Differs in Plant Cells and Animal Cells Plant Cells New Cell Wall and Cell Membrane form from the middle out toward the sides at the plane of division [ Cell Plate]

TELOPHASE

Telophase [continued] Animal Cells: In growing of the Cell Membrane from the perimeter toward the middle [Cleavage Furrow or Invagination of the Membrane]

TELOPHASE

Interphase After Telophase is completed, each of the two genetically identical daughter cells enter G 1 of Interphase and begin the cycle again.