Science Q4

• Cell division


  The process by which a parent cell divides to produce two or more daughter cells
• Types of cell division

  • Mitosis
  • Meiosis
• Mitosis


  The type of cell division that occurs in all other cells in the body
• Meiosis


  The type of cell division that occurs in the sex cells, egg cells in females, and sperm cells in men
• Purpose of cell division

  • Tissue growth
  • Tissue repair
  • Replacement of dying or old cells
• Phases of the cell-division cycle

  • Interphase
  • Mitotic phase
• Interphase

  1. G1 phase

  2. S phase

  3. G2 phase

  4. G0 phase
• G1 phase


  • Cells produce new organelles
  • Increase the supply of proteins
  • Centrioles begin replicating
• S phase


  • DNA replication takes place
• G2 phase


  • Centriole replication is completed
  • Cell continues to grow and prepare for division
• G0 phase


  • Cells stay in a maintenance phase, some cells like nerve and muscle cells do not replicate
• Phases of the M phase (mitotic phase)

  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
• Prophase


  1. Chromatin condenses to form chromosomes

  2. Spindle fibers grow from centrioles

  3. Nuclear membrane disassembles
• Metaphase


  1. Spindle fibers attach to centromeres of chromosomes

  2. Chromosomes align at the equatorial plate
• Anaphase


  1. Centromeres separate

  2. Sister chromatids are pulled to opposite poles

  3. Cytokinesis begins
• Telophase


  1. New nuclear envelope forms

  2. Nucleolus reforms

  3. Spindle fibers break up

  4. Chromosomes uncoil

  5. Cytokinesis continues
• Once the M phase is complete, two new daughter cells are formed and the process of cell division is completed
• Limits to cell growth

  • Stress on DNA
  • Difficulty moving nutrients/wastes across membrane
  • Ratio of surface area to volume
  • Volume increases at a faster rate than surface area
• Cell division


  1. Before cell becomes too large, it divides, producing 2 daughter cells

  2. Each daughter cell is an exact replica of the parent cell

  3. Before cell divides, DNA is replicated, so each new cell will have the same genetic information as the parent cell
• MITOSIS


  Cell divides by copying the DNA - cell splits - new cell with normal number of chromosomes (Cell growth & repair)
• MEIOSIS


  Creates 1/2 sets of chromosomes
• Women = 23 chromosomes, Men = 23 chromosomes, Combined = 46 chromosomes
• Cell division


  Process of cell multiplication, necessary for living system to survive
• Chromosomes


  Threadlike structure within the nucleus containing the genetic information (DNA) that is passed from one generation of cells to the next
• Cells of every organism have a specific number of chromosomes (Fruit flies = 8, Humans = 46, carrots = 18)
• Chromatin


  Granular material visible within the nucleus, consists of DNA tightly coiled around proteins
• Chromatid


  One of two identical "sister" parts of a duplicated chromosome
• Centromere


  An area where the chromatids are attached to one another
• Cell Cycle

  2 major phases: Interphase and Mitosis
• Checkpoint


  One of several points in the eukaryotic cell cycle at which the progression of a cell to the next stage in the cycle can be halted until conditions are favorable
• G1 checkpoint


  Evaluates damage to DNA and other external factors; if conditions are inadequate, the cell will not be allowed to continue to the S phase of interphase
• G2 checkpoint


  Ensures all of the chromosomes have been replicated and that the replicated DNA is not damaged before cell enters mitosis
• M checkpoint


  Determines whether all the sister chromatids are correctly attached to the spindle microtubules before the cell enters the irreversible anaphase stage
• P53


  A signaling protein, also known as tumor suppressor, that halts the cell cycle at G1 when there is DNA damage. It has 3 roles: 1) Halt cell cycle when DNA damage detected, 2) Activate DNA repairing enzymes, 3) Program cell death if damage not fixable.
• Contact inhibition


  A regulatory mechanism that functions to keep cells growing and dividing into a layer one cell thick
• Anchorage dependency


  A requirement for cells to divide; a cell must be anchored to a surface or to other cells
• Benign tumor


  A mass of cells that retain adhesion proteins that keep them properly attached to their home tissue, with no potential to invade other cells
• Malignant tumor


  Includes cells that enable them to spread to other tissues and impair more organs of the body
• Interphase

  3 phases: G1, S, G2
• G1 phase


  Cells do most of their growing, increase in size and synthesize new proteins and organelles