8.2, 8.3: Cell Division and the Cell CycleName:

Levels of Biological organization

  • ______________________________

From zygote to Trillions of Cells

  • ______=Cell that forms when sperm and egg join
  • Called ______
  • Zygote splits into 2 cells which then split into 4, then 8, then 16, etc.
  • Each of these cells contains ______

Why must cells divide?

  • Diffusion ______
  • Cells get materials from surroundings through their membrane. This is also how they expel wastes
  • If the cell gets too large, it would take a long time for these processes to occur
  • ______also limits cell size
  • DNA forms ______
  • There is a limit on how fast this can happen.
  • If the cell is too large, it takes too long to make all of the structures from the proteins.
  • Surface area-to-volume

Cell Cycle

  • ______
  • The cell cycle can be divided into 2 (or 3) stages
  • ______, ______, and ______
  • Interphase and Mitosis are further divided
  • Interphase=______
  • Mitosis=______
  • Neither ______nor ______are technically part of mitosis
  • Interphase (G1, S, G2)
  • “______”
  • ______
  • Period of ______and ______
  • ______(Growth Phase 1/Gap Phase 1)
  • Cell grows in size
  • ______Phase (Synthesis phase)
  • DNA replicates
  • ______(Growth Phase 2/Gap Phase 2)
  • Cell grows again, organelles are duplicated
  • Mitosis
  • Period of ______
  • 4 parts (PMAT)
  • ______(“Prologue”)
  • ______(“Middle”)
  • ______(“Apart”)
  • ______(“Two”)
  • Happens only in ______(body) cells
  • A different process (meiosis) occurs in gametes (sex cells)
  • Prophase (“Prologue”)
  • First and ______
  • ______(unwound DNA) coils around ______(proteins) to become a ______(tightly wound strand of ______and ______)
  • Each copy of DNA (from Interphase) coils and forms 2 identical strands
  • Called ______
  • These sister chromatids join together at the center (called a ______)
  • Each chromosome has a “partner” (remember, you get one from your mom and one from your dad)
  • These are called ______
  • ______disappears
  • ______(pairs of ______) move to opposite ends of the cell
  • ______(“football-shaped”) forms from centrosome
  • Made up of ______
  • These final steps of prophase and early steps of metaphase may be referred to collectively as “______” in some contexts.
  • Metaphase (“Middle”)
  • Spindle fibers ______of chromosomes
  • Spindles extend from centriole on one side and attach to chromatid on that same side
  • Fibers help ______
  • Very important because it ensures that ½ of the chromosomes end up in each cell
  • Anaphase (“Apart”)
  • Spindle fibers shorten and ______at the centromere
  • Each identical sister chromatid ______
  • Telophase (“Two”)
  • Chromatids reach opposite ends
  • ______unwind into ______
  • ______around chromatin
  • ______
  • Cells begin to split
  • This ends Mitosis
  • Cytokinesis
  • Division of ______
  • Cell divides and ______are formed
  • Process differs in plants and animals
  • In plant cells, a structure called a ______forms and separates the 2 daughter cells
  • In animals cells, the cells “pinch in” until the cells are separated
  • A ______forms and the cells split

Control of the Cell cycle

  • During the cell cycle, there are 3 main checkpoints
  • ______(Restriction) Checkpoint
  • Occurs before the cell commits to division
  • Proteins “______” DNA to make sure there are no mutations
  • If it is deemed worthy, the cell commits to division
  • If errors are found, the cycle is stopped,
  • If the error can be fixed, it is
  • If the error cannot be repaired, the cell undergoes apoptosis
  • ______=programmed cell death
  • ______Checkpoint
  • After DNA replication, the cell again checks the DNA for errors
  • Errors are corrected, if possible
  • The cell then enters mitosis
  • If correction cannot occur, the cell undergoes apoptosis
  • ______Checkpoint
  • This checkpoint prevents separation of chromatids if not all are attached to the spindle
  • This would be bad because the daughter cells would not have the correct number of chromosomes
  • We’ll discuss later how this leads to Down’s Syndrome in Meiosis
  • Again, the cell halts mitosis until it can confirm that all chromosomes are connected.
  • If they are all connected, Mitosis resumes
  • If not, the cell attempts to correct it
  • Will undergo apoptosis if not successful
  • When checkpoints fail:
  • If checkpoints stop working, it is possible for ______to cause the cell to divide out of control
  • ______
  • Typically, ______
  • Leads to a ______
  • Cancer cells ______, health cells
  • Causes ______
  • Some cancer cells can also break free and move through the body
  • Called ______
  • The cancer cell then begins to divide in its new location(s)
  • ______tries to halt the cell cycle, stopping the cancer cells from dividing
  • Also halts healthy cells-This is why hair loss is common and why the immune system is suppressed

DRAW THE STAGES OF MITOSIS BELOW

Interphase ProphaseMetaphaseAnaphase TelophaseCytokinesis