1. Mitosis Unit 4: Cellular Processes

2. Background 1. Most plant and animal cells reproduce asexually - no DNA swap between other cells a. This means the cells produced are exact copies or clones of the original cell. b. The number of cells changes, but the DNA does not. 2. Binary Fission : cellular division of unicellular organisms that produces identical offspring a. This is how Prokaryotes reproduce

3. 3. Why do cells reproduce? a. Increase size of organism b. Repair injuries c. Replace worn out cells

4. 4. Pros and Cons of Asexual Reproduction A. Pro i. Can produce offspring more quickly ii. Can produce offspring more easily iii. Do not need a partner cell to reproduce B. Con i. All cells are alike ii. Species can’t change and adapt iii. Do not need a partner cell to reproduce iv. One disease can wipe out a whole population

5. Eukaryotic Life Cycle a. Eukaryotic life cycle called the “cell cycle” b. Consists of 6 “phases” i. Interphase ii. Prophase iii. Metaphase iv. Anaphase v. Telophase vi. Cytokinesis c. The cell is usually in Interphase (about 90% of cells are in this phase at any given time!) i. Nerve cells can stay in this phase for decades I P ray AT C hurch

6. Visualize the Cell Cycle: Interphase Mitotic Phase (M Phase) C Phase G1 G2 S (or G 0 ) Prophase Metaphase Anaphse Telophase Cytokinesis

7. 6.Interphase a. This is when the cell is under “normal” conditions b. No cell division occurs at this time c. Cell obtains nutrients and duplicates its chromatids. i. Chromatids are connected by a centromere ii. Have a long and short arm d. Comprised of a few “sub phases”: i. G1 ii. S Phase iii. G2 iv. G0

8. Chromosome Stuff

9. 7. G1 a. G1: Means “growth 1” b. Cell creates organelles and begins metabolism c. Occurs after a new “daughter cell” has been created (cytokinesis) and before S Phase d. Major period of cell growth e. New organelles are synthesized i. Lots of protein synthesis occurs Provide structural support and enzymes catalyze reactions to make new organelles

10. 8. S Phase a. S phase: means synthesis phase b. Between G1 and G2 c. DNA synthesis (replication) occurs during this phase d. Chromosomes in the cell are copied e. Each chromosome has one coiled DNA double helix, called a chromatid f. At the end of this phase, each chromosome has two identical DNA double helix molecules i. Makes 2 sister chromatids ii. Centrosome is also duplicated

11. 9. G2 a. G2: means growth 2 b. Shortest part of interphase, occurs after S phase and usually lasts around 4-5 hours. c. Even though chromosomes copied, hard to find distinct chromosomes i. Chromosomes are still in the form of loosely packed chromatin fibers. d. Cell grows in preparation for cell division (Mitosis)

12. 10. G0 a. Sometimes the cell exits the cell cycle into a state called “G0” i. Usually happens from G1 b. Cells are alive and metabolically active c. But cells do NOT: i. Divide ii. Copy DNA iii. Prepare for cell division d. Examples of cells in G0 phase: i. Heart muscle cells ii. Eye cells iii. Brain cells e. If these cells are damaged, they can not be replaced.

13. 11. What IS Mitosis? a. Mitosis occurs when a cell needs to reproduce itself i. Most often happens in Eukaryotic cells b. Makes 2 cells that are genetically identical to their “parent” cell and to each other (like twins) i. We call this “2n” cells ii. Mitosis makes s omatic (body) cells c. Mitosis is usually followed by cytokinesis (cell splits into 2 daughter cells) i. Together, these make up “ M Phase ”

14. Important Structures Asters Centrioles Polar Fibers Kinetechore Fibers Equator Kinetechore

15. 12.Prophase a. DNA Compresses into Chromosomes b. Centrioles appear in centrosome region & move to poles i. Centrosome organizes spindle c. Nuclear membrane & nucleolus disappear d. Spindle fibers form & attach to chromosomes

16. 13.Metaphse A. Chomosomes line up in the middle of the cell B. Think M eta- M iddle

17. 14. Anaphase a. Centromeres split chromatids and move them apart

18. 15.Telphase a. Reverse Prophase b. Two nuclei form c. Nuclear membrane and nucleolus returns d. Centrioles and spindle fibers disappear e. DNA spreads out as chromatin

19. 16. Cytokinesis Cytoplasm splits into 2 cells