Cell Growth and Reproduction Cells grow and then

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 • G 1 (growth 1) • S ( synthesis) • G 2 (growth 2)

G 1(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

G 2 (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

Chromosomes Centrioles 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. mcgrawhill. com/sites/0072495855/student_view 0/chapter 2/animation__mitosis_and_cytokinesis. html

2 Daughter cells