Review Why do cells divide?? Big cells are inefficient! Nutrients can’t reach the organelles! Volume increases much faster than surface area! Proteins can’t be synthesized quickly enough!
Before Cells Divide… • INTERPHASE! • Cells carry out normal functions • Most of a cell’s time is spent in this phase • 3 parts! G1, S, and G2
G1 PHASE • DNA stored as chromatin loose and unwound • Cell grows and organelles replicate S PHASE • Synthesis • DNA replicates G2 PHASE • Rapid growth before division
Now the cell is ready to divide! • MITOSIS: The division of the nucleus! • 4 Phases!
PROPHASE • DNA condenses into chromosomes • Nucleus disappears • Spindle fibers form • Centrioles move to side
METAPHASE • Chromosomes line up down the middle of the cell • Spindle fibers attach to centromere
ANAPHASE • Chromatids separate • Spindle fibers pull chromosomes to the sides
TELOPHASE • Cleavage Furrow forms • Nucleus reforms • DNA unravels • Centrioles and spindle fibers disappear
Quick Mitosis Summary… • Mitosis Division of the nucleus • 1 Prophase • 2 Metaphase • 3 Anaphase • 4 Telophase • Ready for the last part of the cell cycle???
CYTOKINESIS! • Division of the cytoplasm • Cell splits into 2 new cells! • NOT a part of mitosis Cleavage Furrow Cell Plate