The cell cycle


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The cell cycle

  1. 1. The Cell Cycle
  2. 2. In the time that it takes you to readthis sentence, your body will have made millions ofnew cells! Making new cells allows you to grow and replace cells that have died.
  3. 3. The Life of a Cell Cell cycle: the life cycle of a cell Cell cycle begins when the cell is formed and ends when the cell divides and forms new cells Before a cell divides, it must make a copy of its DNA
  4. 4.  DNA is organized into structures called CHROMOSOMES Copying chromosomes ensures that each new cell will be an exact copy of its parent cell
  5. 5. How does a cell make more cells? Depends on whether it’s prokaryotic (no nucleus) or eukaryotic (with nucleus)
  6. 6. Making More Prokaryotic Cells Prokaryotic cells are less complex than eukaryotic cells Cell division is called “binary fission”, which means “splitting into two parts” Binary fission results in two cells that each contain one copy of the circle of DNA
  7. 7. Eukaryotic Cells and Their DNA Eukaryotic cells are more complex The chromosomes of eukaryotic cells contain more DNA than prokaryotic cells
  8. 8.  Different kinds of eukaryotes have different numbers of chromosomes Example: humans have 46 chromosomes
  9. 9. Think “more chromosomes = better organism”?Not true! Humans have 46, but a lot of organisms have more than us! Butterfly = 380 Goldfish = 94 Horse = 64 Amoeba = 40 Tobacco plant = 48
  10. 10.  Homologous chromosomes: chromosomes that have the same sequence of genes and the same structure
  11. 11. Making More Eukaryotic Cells The eukaryotic cell cycle includes 3 stages:1. Interphase: cell grows and copies its organelles and chromosomes2. Mitosis: complicated process of chromosome separation3. Cytokinesis: cell splits into two cells; these cells are identical to each other
  12. 12. Mitosis•Cell division occurs in a series of stages, or phases
  13. 13. 1st: INTERPHASE  Chromosomes are copied (# doubles)  Chromosomes appear as threadlike coils (chromatin) at the start, but each chromosome and its copy (sister chromosome) change centromere to sister chromatids at end of this phase
  14. 14. 2 : PROPHASEnd  Mitosis begins (cell begins to divide)  Centrioles (or poles) appear and begin to move to opposite sides of cell  Spindle fibers form between the poles
  15. 15. 3 : METAPHASErd  Chromatids (or pairs of chromosomes) attach to the spindle fibers
  16. 16. 4 : ANAPHASEth  Chromatids (or pairs of chromosomes) separate and begin to move to opposite ends of the cell
  17. 17. 5 : th TELOPHASE  Two new nuclei form  Chromosomes appear as chromatin (threads rather than rods)  Mitosis ends
  18. 18. 6 : CYTOKINESISth  Cell membrane moves inward to create two daughter cells – each with its own nucleus with identical chromosomes
  19. 19. Ways to Remember the Order of Mitosis!I Proposed Marriage After Tuesday’s Class.I Picked Marigolds After Typing Class. Can you think of any?