The Cell Cycle & Mitosis

Cellular Division 101

The Cell Cycle

The Cell Cycle The cell cycle is the series of events that

occur in a cell including growth, replication and division.

There are two major divisions: Interphase Mitotic Phase (Mitosis and Cytokinesis)

Interphase

Interphase Interphase is where cells spend most of their

lives. Interphase is the time between cell divisions. There are three phases to Interphase.

G1 – Cell growth S – DNA is copied G2 – Growth continues and preparation for division

begins.

What is Mitosis?

What is Mitosis? Mitosis is the division of the nucleus of a cell

with duplicated DNA In mitosis, a parent cell divides into two

diploid daughter cells Four steps: Prophase, Metaphase,

Anaphase, Telophase

Prophase

Prophase

Chromatin condenses to form chromosomes

Nuclear envelope dissolves Centrosomes move to opposite ends of

the cell Spindle forms between centrosomes

and chromosomes start to move to the center

Metaphase

Metaphase

Chromosomes line up across the center of the cell

Chromosomes attach to the spindle fibers

Anaphase

Anaphase Centromeres divide Sister chromatids move rapidly to opposite

poles

Telophase

Telophase Chromosomes return to chromatin form Spindle fibers disappear Nuclear envelope begins to form around each

set of chromosomes

Cytokinesis

Cytokinesis The process by which cells divide.

Animal cells: cleavage furrow. Area of the cell membrane pinches in

Plant cells: cell plate. Vesicles from the Golgi apparatus join together at the

midline of the cell to form a cell wall

Two daughter cells are about the same size. Each receives half the cytoplasm and half the

organelles.

Prophase

Metaphase

Anaphase

Telophase

Control of Cell Division

Control of Cell Division Think traffic lights – green means go, while red means

stop. Three checkpoints in the cell decide whether the cell should

“stop” or “go”. Cell Growth Checkpoint (G1)

Is the cell large enough? Is it healthy? Green light sends us into DNA replication.

DNA Synthesis Checkpoint (G2) Did DNA replicate correctly? Green sends the cell into

Mitosis. Mitosis Checkpoint

Did mitosis go okay? Green sends the cells exiting mitosis.