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February 26, 2015
Objective: Model the stages of mitosis Explain the cell cycle
Journal: Why are cells small?
The Cell Cycle
The Cell Cycle
Four Phases G1 – Gap 1 S – DNA Replication G2 – Gap 2 Mitosis
Interphase
Occurs when the cell is not dividing Cells spend the majority of their time in this phase Made up of three phases
G1 – Growth Phase S – DNA Replication Occurs
Chromatin replicates to form sister chromatids G2 – Growth Phase
Interphase continued…
During G2, specialized structures are made: Centrioles – help to make spindle fibers Spindle fibers – strings that attach to
chromosomes and help move them within the cell
Mitosis
Division of the nucleus
Occurs in 4 stages: PMAT Prophase Metaphase Anaphase Telophase
http://www.stolaf.edu/people/giannini/flashanimat/celldivision/crome3.swf
1st: Prophase
Mitosis begins and cell begins to divide
Centrioles begin to move to opposite ends of cell
Spindle fibers form from the centrioles
Prophase
2nd: Metaphase
Sister Chromatids or pairs of chromosomes line up at the center of the cell and attach to the spindle fibers
Metaphase
3rd: Anaphase
Sister chromatids separate and begin to move to opposite ends of the cell
Anaphase
4th: Telophase
Two new nuclei form around the chromosomes
Chromosomes become chromatin (threads rather than X’s)
Mitosis ends
Telophase
Cytokinesis
Last stage of the cell cycle Not part of mitosis
Cell membrane pinches inwards to create two daughter cells – each with its own nucleus with identical chromosomes
Cytokinesis