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