CELL CYCLE

1. CELL CYCLE Chapter 8 Bio 391

2. Nucleic Acids – A Review • Class of macromolecule • Monomer = nucleotide • Phosphate • Sugar • Nitrogenous base • Determine order of amino acids • Source of genetic information which is passed between generations

3. Nucleic Acids – A Review Types • DNA • Double stranded • Deoxyribose • Bases: • Cytosine, guanine, adenine, thymine • RNA • Single stranded • Ribose • Bases: • Cytosine, guanine, adenine, uracil

4. Discovering DNA Rosalind Franklin Watson & Crick Franklin noticed a diffraction pattern in DNA that showed that DNA was 2-stranded and a helix-shape Watson & Crick: used these notes to construct the famous model

5. Nucleotide Arrangement Nucleotides are the building blocks of DNA Phosphate Sugar Base

8. What is a chromosome?

9. Chromosomes • Structures that carry genetic information • Made up of DNA and protein (histones) • DNA coils very tightly around histones degree of coiling leads to whether DNA is visible or invisible • Each eukaryote has a characteristic number of chromosomes in the nucleus of each cell. • Examples: • Humans- 46 • Dog- 78 • Housefly- 12 • Potato plant- 48 • Cat- 38 • Aspergillus (fungus)- 8 • Drosophila (fly) - 8

10. Chromosomes • While the cell is “resting”, you cannot see the chromosomes • It is unwound Called chromatin • While the cell is dividing, you can see the chromosomes • Wound up Made of two sister chromatids connected by a centromere

11. Intro videos http://www.youtube.com/watch?v=eFuCE22agyM Synchronized swimming http://www.youtube.com/watch?v=3kpR5RSJ7SA&e Teaching http://www.youtube.com/watch?v=-mWUpdxIDrc&e song http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__mitosis_and_cytokinesis.html Talking textbook

12. Cell Division in Eukaryotes • Multicellular organisms grow larger and replace damaged or dead cells through the process of cell division. • Why must cells split and divide? Why can’t cells just grow larger? • Surface area-to-volume ratio • How does the cell cycle compare in various organisms? • Prokaryotic vs. eukaryotic

13. 8.2 The Phases of the Cell Cycle • The cell cycle is the complete series of events from one cell division to the next. • When a cell no longer has enough surface area (contact with the outside) to support its volume (what needs to be accomplished inside) the cell must divide and become two cells. • Two resulting cells are called daughter cells • Phases of the Cell cycle: • G1 (Gap 1) • S phase (synthesis) • G2 (Gap 2) • Mitosis (actual cell division)

15. INTERPHASE • The time between one cell division to the next • Chromosomes are not visible • Includes G1, S and G2 • G1- preparation for synthesis, normal cell functions, synthesis of RNA or other macromolecules • S- replication of DNA • G2- preparation for mitosis

16. G zero (G0) • Many times a cell will leave the cell cycle, temporarily or permanently. • It exits the cycle at G1 and enters a stage designated G0 (G zero). A G0 cell is often called "quiescent“ (a state of arrest, inactive). • G0 cells are anything but quiescent. They are busy carrying out their functions in the organism • Some will never reenter the cell cycle but instead will carry out their function in the organism until they die. Others can be triggered to reenter the cycle and produce more cells • Ex: cardiac, most nerve cells, red blood cells • Cancer cells cannot enter G0 and are destined to repeat the cell cycle indefinitely.

17. Cell Cycle Rates Cells do not move through the cell cycle at the same rate • Different types of cells spend different amounts of time within each phase • Once a cell pass “the restriction point” it must continue on through the cell cycle and it cannot return to G1 or G0 • Cells in a developing embryo replicate rapidly- 3 minutes • Average time of cell cycle- 20 hours • Lining of esophagus- 2-3 days • Lining of small intestine- 1-2 days • Lining of large intestine- 6 days • Red blood cells-120 days • White blood cells- 10hrs-decades

19. http://www.cellsalive.com/cell_cycle.htm

20. The Stages of Cell Division • Prophase • Nuclear membrane breaks down • Chromosomes condense • Microtubules from the mitotic spindle • Centrioles move to opposite sides of the cell (plants DO NOT have centrioles- the centrosome is used instead) • The microtubules connect the kinetochore of each sister chromatid to the spindle poles around each centriole Spindle forming Centromere Chromosomes (paired chromatids)

21. The Stages of Cell Division • Metaphase • Spindles move chromosomes to the metaphase plate, perpendicular to the poles down the center of the cell • Think Metaphase- Middle Centriole Spindle Centriole

22. The Stages of Cell Division • Anaphase • Enzymes break down the connection of the sister chromatids at the centromere • Sister chromatids are pulled apart to opposite ends of the cell • Sister chromatids are now called Chromosomes Individual chromosomes

23. The Stages of Cell Division • Telophase • Chromosomes begin to expand • Nuclear envelope reappears making two nuclei Nuclear envelope reforming

24. The Stages of Cell Division • Cytokinesis • Divides the cell in two • In animals: plasma membrane pinches in forming a cleavage furrow until the cell completely pinches apart into two separate cells • Begins during anaphase • In plants: cell plate forms down center of cell and ultimately forms two separate cells • Begins during telophase

27. Control of the Cell Cycle Cyclins • Regulate progression through the cell cycle by increasing and then decreasing in number • Act by binding to kinases Kinases • Enzymes that activate other enzymes or proteins using ATP • Amount remains steady throughout cell cycle • Called CDKs (cyclin dependent kinases)

28. Hypothesis: Substance X will cause a cell to start mitosisSubstance X = CYCLIN Section 10-3 The sample is injected into a second cell in G2 of interphase. A sample of cytoplasm is removed from a cell in mitosis. As a result, the second cell enters mitosis. Cyclin cellular protein that regulates the timing of the cell cycle in eukaryotic cells;  help create spindle

29. CDK + cyclin = active kinase • Active kinase is able to activate enzymes and proteins necessary for certain stages to the cell cycle to progress • When active kinase is no longer needed, levels of cyclin drop, cyclins and CDK break apart and that phase of the cell cycle ends

30. Cell Cycle Regulators

31. Checkpoints • Things can go wrong during the cell cycle. If these problems go unchecked or uncorrected serious problems could result in the organism • Specific proteins detect mistakes and the cell cycle is halted until the mistake is fixed • Ex: p53 • Inactivates formation of G1 cyclin-kinase system • Gene responsible for halting the cell cycle until all chromosomes have replicated properly • Defects in this gene is a precursor to cancer

33. Cancer Genes • Proto-oncogenes promote cell division while tumor suppressors inhibit cell division • In cancer cells both pathways are disrupted. • Mutated proto-oncogene= oncogene (cancer gene) • Oncogene causes cells to leave G0 and proceed through cell division • Mutated tumor suppressor genes causes removal of checkpoint system • Cells continue to divide repeatedly • Cancer cells metastasize (spread throughout the body)

34. Progression of Cancer

36. US Mortality, 2003 No. of deaths % of all deaths Rank Cause of Death 1. Heart Diseases 685,089 28.0 2. Cancer556,902 22.7 3. Cerebrovascular diseases 157,689 6.4 4. Chronic lower respiratory diseases 126,382 5.2 5. Accidents (Unintentional injuries) 109,277 4.5 6. Diabetes mellitus 74,219 3.0 7. Influenza and pneumonia 65,163 2.7 8. Alzheimer disease 63,457 2.6 • Nephritis 42,453 1.7 10. Septicemia 34,069 1.4 Source: US Mortality Public Use Data Tape 2003, National Center for Health Statistics, Centers for Disease Control and Prevention, 2006.