Cell Growth and Reproduction Cells grow and then reproduce Worn-out cells are repaired or replaced by new cells Cells grow in a cycle, called the Cell Cycle

Cell Cycle 2 general periods 1) Growth (Interphase) 2) Division (mitosis)

MITOSIS Cell division is called Mitosis Mitosis has 4 phases: Prophase, Metaphase, Anaphase, Telophase Result: 2 genetically identical daughter cells

Interphase During this phase the Cell grows in size and Carries on metabolism Chromosomes (structures that carry DNA) are duplicated

Interphase Divided into 3 parts G1 (growth 1) S ( synthesis)

G1(growth 1) A time of rapid growth and metabolic activity Protein production is high Organelles are beginning to be made

S (synthesis) DNA (deoxyribonucleic acid) is synthesized and replicated The cell copies its chromosomes

G2 (growth 2) Mitochondria and other organelles are made Centrioles (contractile tubules), replicate The last stop before a cell divides (is mitosis)

Chromosomes Carry DNA on them When they are not getting ready for cell division, chromosomes exist at chromatin Chromatin is long strands of DNA wrapped around proteins

The 2 halves of chromosomes are called Sister Chromatids Sister Chromatids and the DNA they contain are exact copies of each other

Mitosis: Cell Division

4 Phases of Mitosis 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase

Prophase Chromatin coils into visible chromosomes Nucleus disappears Nuclear envelope and nucleolus disintegrate Centrioles (only present in animals) begin to migrate to opposite ends of the cell (poles) A spindle begins to form, which plays a role in the separation of sister chromatids

Nucleus Centrioles Nuclear Envelope Spindle Fibers Chromosomes

Metaphase Short phase Chromosomes become attached to the spindle fiber by their centromere Chromosomes begin to line up in the middle of the cell, called the equator META = MIDDLE

centrioles Chromosomes Spindle Centromere

Anaphase Sister Chromatids begin to separate The centromeres split apart ANA = APART

Centrioles Sister Chromatids Split apart Spindle

Telophase Sister Chromatids reach the opposite poles of the cell Spindle begins to breakdown Nucleus reappears Nuclear envelope forms around each set of chromosomes

Telophase In plants, a cell plate is formed In animals the cell “pinches” in along the equator, which is called a Cleavage furrow

Centrioles Chromosomes Nucleus The animal Cell “pinches” in at the equator Nuclear Membrane

Cytokinesis The cell’s cytoplasm divides Result: 2 Daughter Cells that are GENETICALLY IDENTICAL http://highered.mcgraw- hill.com/sites/0072495855/student_view0/chapter2/animation__mitosis_and_cytokinesis.html

2 Daughter cells