Cell CycleLife of a Eukaryotic Cell

Cell Cycle

(Interphase in Red)

G1 – cell grows & carries out major functions

S – DNA is copied

G2 – Prep for mitosis; organelles reproduced

Mitosis – Nucleus divided into two nuclei, each with same number and kind of chromosomes

Cytokinesis – cytoplasm divides

Cell Cycle ControlHow does cell “know” when to divide?

Cell cycle controlled by many proteins (enzymes) at three main checkpoints:G1 checkpoint – decision made whether cell will

divide (cell healthy and large enough). Some types of cell never pass this point (nerve, muscle)

G2 checkpoint – Did DNA replication go OK? If so, go on to mitosis

Mitosis checkpoint – Is mitosis over? If so, head to G1 phase

Cancer - What happens if control is lost

Cancer = uncontrolled cell growth

Disorder of cell division

Control mechanisms don’t work (gene for proteins that control cell cycle are defective)

Mutations:

Overproduction of growth-promoting hormones – speeds up cell cycle

Inactivation the control proteins that act to slow or stop cell cycle

Mitosis and Cytokinesis Chromatids are

physically moved to opposite sides of dividing cells with help of spindle fibers

Centrosome (in animals) – made up of two centrioles - organizes assembly of spindle fibers

Spindle fibers made from microtubules

Mitosis and Cytokinesis Chromatids separate by

attaching spindle fibers

Spindle fibers attach to centromeres of chromosomes

Paired chromatids separate. One chromatid goes to one pole of the cell, the other chromatid goes to the other as the spindle fibers shorten

Interphase (90% of cell’s time)Mitosis (nuclear division)

ProphaseMetaphaseAnaphaseTelophase

Cytokinesis (cytoplasmic division)

Watch video clip of mitosis

Another View of Mitosis

Mitosis Foldable6 sheets of paper

Follow teacher’s instructions to construct booklet

You will make foldable based on pictures and descriptions of interphase, cyokinesis, and mitosis in your book (p. 125 and pp 130 – 132)

Include sketches and textual descriptions in foldable

You can also use www.cellsalive.com and www.biology.arizona.edu/cell_bio/tutorials/cell_cycle/main.html

Headings for foldableCover = Phases of Somatic Cell Division

Following sheets – Interphase

G1 S G2

Mitosis Prophase Metaphase Anaphase Telophase

Cytokinesis

HomeworkRead Ch. 7 – “Meiosis and Sexual Reproduction”

Also read about plant reproduction pp. 534 – 535, and pp. 538 – 539

Complete Guided Reading packet for Chapter 7

Complete Foldable