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Cell Cycle and Mitosis and Loss of Cell Cycle Control Targets 7-14.

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Presentation on theme: "Cell Cycle and Mitosis and Loss of Cell Cycle Control Targets 7-14."— Presentation transcript:

1 Cell Cycle and Mitosis and Loss of Cell Cycle Control Targets 7-14

2 A cell cycle is: the regular sequence of growth and division that cells undergo.  There are three main stages during a cell cycle: Stage 1= Interphase Stage 2= Mitosis (Prophase, Metaphase, Anaphase, Telophase) Stage 3= Cytokinesis

3 This figure represents the amount of time that each stage of the cell cycle takes G1 S G2 Interphase Mitosis Cytokinesis P M A T

4 Stage 1: Interphase (3 parts)  During this stage, a cell grows, copies its chromosomes, and prepares to divide. 1. G 1 : most of cell’s life is spent here in growth and development. 2. S (synthesis): Chromosomes (in the form of chromatin) are copied in the nucleus = DNA replication, centrioles are also copied. 3. G 2 : Cell continues to grow, copies cell organelles, prepares to divide. This part of cell cycle lasts the longest—cell spends the majority of its life here!

5 Checkpoint Animation hill.com/sites/ /student_view0/chapter2 /animation__control_of_the_cell_cycle.html

6  There are checkpoints to control the rate that cells go through the cell cycle.  2 of the 3 checkpoints occur during interphase: G 1 checkpoint: most important checkpoint; cells are stopped during G 1, and must receive signals in order to continue on to the S phase. ○ If the cell does not receive a go-ahead signal, it will exit the cell cycle and go to G 0, a non-dividing state (mature nerve cells and muscle cells typically do this!). G 2 checkpoint: makes sure that DNA has been replicate correctly during the S phase. Passes on to mitosis if DNA replication happens correctly

7 This figure represents the area of each checkpoint G1 S G2 Interphase Mitosis Cytokinesis P M A T G2 Checkpoint G1 Checkpoint

8 Stage 2: Mitosis  During this stage, a cell’s nucleus divides into 2 new nuclei (4 phases in mitosis).  Mitosis checkpoint: makes sure a complete set of chromosomes will go into each daughter cell. If all is well-passes on to cytokinesis

9 This figure represents the area of each checkpoint G1 S G2 Interphase Mitosis Cytokinesis P M A T M Checkpoint G2 Checkpoint G1 Checkpoint

10 Cells Alive Animation…

11 1. Prophase: a) Chromatin condenses into chromosomes (with sister chromatids attached by centromeres). b) Nuclear membrane starts to break down. c) Centrioles begin to separate to opposite ends of the cell and spindle fibers form from the centrioles. Animal Cells

12 Plant Cell Prophase

13 2. Metaphase: a) Centrioles are at opposite ends of cell. b) Sister chromatids line up in center of cell and attach to spindle fibers at their kinetochores within the centromeres. Animal Cells

14 Plant Cell Metaphase

15 3. Anaphase: a) Chromatids are pulled apart at the centromere. b) Spindle fibers pull chromatids toward opposite ends of cell (to centrioles). Animal Cells

16 Plant Cell Anaphase

17 4. Telophase: a) New nuclear membranes form around chromosomes at each end of cell. b) Chromosomes reach opposite ends of the cell c) The Chromosomes uncoil into chromatin Animal Cells

18 Plant Cell Telophase Early TelophaseLate Telophase

19 Stage 3: Cytokinesis  During this stage, the cytoplasm completely divides to make 2 new identical cells. The cell’s organelles are divided between the 2 new cells. In animal cells, the cleavage furrow completely pinches in to make 2 cells. In plant cells, the cell plate becomes the cell wall and completely separates the 2 cells. At the end of cytokinesis, 2 new identical daughter cells are formed! Mitosis animation

20

21 This figure represents the amount of time that each stage of the cell cycle takes as well the various checkpoints. G1 S G2 Interphase Mitosis Cytokinesis P M A T M Checkpoint G2 Checkpoint G1 Checkpoint

22 Cells Alive Animation

23 Objectives 12-13

24 Normal Cell Characteristics 1) Density Dependent Inhibition – crowding of cells causes them to STOP dividing In the picture, cells will divide until a single layer forms along the bottom If you take out some cells, they will divide until the bottom is full again 2) Anchorage Dependence – cells must be attached to something (like the bottom of a container or extracellular fibers)

25 Cancer Cell Characteristics 1) Lack Density Dependent Inhibition – crowding of cells DOES NOT cause them to STOP dividing In the picture, cells will continue to divide, piling on top of each other 2) Do NOT exhibit Anchorage Dependence – cells DO NOT have to be attached to anything

26 Benign Tumors v. Malignant Tumors  Benign - abnormal cells remain the original site of development (lump) = do NOT cause serious problems and can be removed (usually)  Malignant – abnormal cells have divided often and have spread to surrounding area = CANCER May have a strange number of chromosomes No longer function productively Secrete molecules to tell the blood vessels to grow to them to “feed” them Metastasis - cells lose attachment to other cells, travel in the blood stream, and divide uncontrollably in a new location = the cancer has SPREAD

27 Cancer Treatments  Radiation – treats localized cancer with high- energy waves Damages cancer DNA more than normal DNA due to cancer DNA’s inability to fix the errors (normal cells can fix the damage)  Chemotherapy – treats unknown cancer or cancer that has metastasized Damages actively dividing cells (like cancer cells) ○ explains why your hair falls out, why you feel sick and why your immune system is lowered, but you can continue to function Example : the drug Taxol freezes the spindles and stops cell division during metaphase

28 Alternative Cancer Treatments  Gene Therapy – insert genetic material (DNA or RNA) into cells to fight or prevent disease  Targeted cancer therapy – drugs that target molecules that are ONLY present on cancer cells to prevent dividing ies/breast/main.html#


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