The Cell Cycle PDF

THE CELL CYCLE CHAPTER 4 SECTION 3 : PAGES 98 - 101  INTRODUCTION: Making new cells allows you to grow and replace cells that have died. Your body is constantly making new cells! As we pass through different stages on life, cells also pass through different stages in their life cycle....

THE CELL CYCLE CHAPTER 4 SECTION 3 : PAGES 98 - 101  INTRODUCTION: Making new cells allows you to grow and replace cells that have died. Your body is constantly making new cells! As we pass through different stages on life, cells also pass through different stages in their life cycle. Cell Cycle: is the life cycle of a cell. The cell cycle begins when the cell is formed and ends when the cell divides and forms new cells.  THE LIFE OF A CELL: Before a cell divides, it must make a copy of its DNA (ensures that each new cell will be an exact copy of its parent cell). DNA is organized into structures called chromosomes, How? 1- Nucleus contains chromosomes. 2- Chromosomes contains DNA + Protein (called chromatin).  MAKING MORE PROKARYOTIC CELLS Cell division in bacteria is called binary fission, which means “splitting into two parts.” Bacteria have a single circular DNA molecule (chromosome), Duplicat ion of exist without nucleus (prokaryotic cell). DNA Binary fission results in two cells that each contain one copy Divisi on of the circle of DNA. New cells  EUKARYOTIC CELLS AND THEIR DNA The chromosomes of eukaryotic cells contain more DNA than those of prokaryotic cells (more complex). Different kind of eukaryotes have different numbers of chromosomes, Example: Fruit flies have 8 chromosomes, potatoes have 48, and humans have 46. Pairs of similar chromosomes are called homologous chromosomes. Humans have 46 chromosomes arranged in 23 pairs.  MAKING MORE EUKARYOTIC CELLS The cell cycle has three stages: 1- Interphase: the cell grows and copies its chromosomes for duplication. The two copies of chromosomes are now called chromatids. 2- Mitosis: the process of cell division (4 phases), by which chromatids separate to form new chromosomes with the same number in each cell. 3- Cytokinesis: splitting into two identical cells by division of cytoplasm. Interph ase  MITOSIS AND THE CELL CYCLE Mitosis has four phases: Prophase. Metaphase. Anaphase. Telophase. Then happens: cytokinesis. MITOSIS WITH EXPLANATION Figure 4 page 100 Sister chromatids are formed Sister chromatids are aligned in (after each chromosomes make the center of the cell + Nuclear another copy of itself in membrane starts to disappear. Interphase).  MITOSIS WITH EXPLANATION Figure 4 page 101 Sister chromatids split to make Formation of new nucleus (two Splitting into two identical cells by new chromosome of each one nucleus) + the cell elongates to division of cytoplasm and cell (daughter chromosomes). divide later. membrane.  CYTOKINESIS CYTOKINESIS: splitting into two identical cells by division of cytoplasm. In cells that do not contain a cell wall (Animal cells): Division of cytoplasm begins at the cell membrane. The cell membrane pinches off so two daughter cells can be formed. In cells that contain a cell wall (Plant cells): A cell plate forms in the middle of the cell. After the cell splits into two, a new cell wall forms where the cell plate was. Cell