CELL CYCLEDr. Brasington

SOMATIC CELL DIVISION

The process of a cell dividing into 2 identical daughter cells.

Occurs when cells reach a certain age A means of body growth, replacing older

cells, and repairing injured parts of the body. 3 stages: interphase, mitosis, and

cytokinesis.

INTERPHASE

Cells spend most of their time in interphase. Subdivided into G1, S, G2. G0? G1: Cell grows larger S: Chromosomes are duplicated and the

amount of DNA doubles. G2: More growth and cell prepares for

mitosis. Mitosis: The division of the nucleus to

produce 2 diploid nuclei. -Occurs at the END of interphase.

PHASES OF MITOSIS

Prophase Metaphase Anaphase Telophase

PROPHASE

The nuclear membrane disappears. The spindle apparatus begins to form. The chromosomes (comprised of 2 sister

chromatids)condense .

PROPHASE

METAPHASE

Chromosomes line up at the equator at the metaphase plate.

Centrioles align at opposite poles. Microtubules that make up the spindle fibers

extend from the poles to the center of the cell.

Chromosomes move randomly until they attach at their kinetochores to polar fibers from both sides of their centromeres.

Kinetochores: Protein structure where spindle fibers attach to pull sister chromatids apart.

METAPHASE

METAPHASE

ANAPHASE The paired centromeres begin to move apart. Once the paired sister chromatids separate from

one another, each is considered a “full” chromosome “daughter chromosomes”.

Through the spindle apparatus, the daughter chromosomes move to the poles at opposite ends of the cell.

The 2 poles of the cell also begin to move apart. At the end of anaphase, each pole has a complete

compilation of chromosomes.

ANAPHASE

ANAPHASE

ANAPHASE

TELOPHASE

Nuclei begin to form at opposite poles. Nuclear envelopes are formed . Nucleoli reappear. Chromatin fibers of the chromosomes uncoil. Spindle fibers and centrioles disappear. Cytokinesis. Completion of the cycle marks beginning of

life cycle for the 2 daughters. Life cycle ends when the 2 daughters divide again.

TELOPHASE

TELOPHASE

THE END