CELL DIVISION Chapter 10-2
CELL DIVISION • Chromosomes are not visible in cells until cells begin the process of cell division.
CELL DIVISION • Chromosomes consist of two identical sister chromatids.
CELL DIVISION • A centromere holds the two sister chromatids together at their centers.
CELL DIVISION • Cell Cycle • The cell goes through a stage called interphase between cell divisions.
The Cell Cycle • Cells grow and then divide in a series of events called the cell cycle.
The Cell Cycle • M phase is the when the nucleus divides.
The Cell Cycle • Interphase consists of: • G1 phase • S phase • G2 phase
The Cell Cycle • G1 phase - cells do most of their growing.
The Cell Cycle • S phase
The Cell Cycle • G2 phase
Mitosis • Four phases: • Prophase • Metaphase • Anaphase • Telophase
Mitosis • Centrioles are the tiny structures located in the cytoplasm near the nuclear envelope at the beginning of prophase.
Mitosis • Spindle – is the fanlike microtuble structure that helps separate the chromosomes.
Mitosis • During Prophase: • the chromosomes become visible in the nucleus; • the centrioles take up positions on opposite sides of the nucleus.
Mitosis • During Metaphase: • The chromosomes line up in the center of the cell.
Mitosis • During Anaphase : • The chromosomes move until they form two separate • Forming groups at opposite poles of the spindle.
Mitosis • During Telophase: • the nuclear envelope re-forms around each cluster of chromosomes; • the nucleolus becomes visible in each daughter nucleus.
Cytokinesis • Cytokinesis is the division of the cytoplasm.
Cytokinesis • How does it happen in animals? • The membrane is drawn downward until it is pinched into nearly two equal parts.
Cytokinesis • A cell plate is formed midway between the divided nucleus during cytokinesis in plant cells.