Unit Three “Cell Proliferation and Genetics”

1. Unit Three“Cell Proliferation and Genetics” “Mitosis”

2. Prokaryotic Cell Cycle • Prokaryotic cell division occurs in two stages, which together comprise a “Simple Cell Cycle” • A) DNA Replication • B) Cell divides in process known as “Binary Fission” *** Each new cell contains one chromosome and is a complete prokaryotic organism

3. Eukaryotic Cell Cycle • The eukaryotic cell cycle is much more complex than that of prokaryotes due to the following factors: • 1. cells are larger • 2. many more organelles • 3. much more DNA arranged in linear segments known as “Chromosomes” • 4. cell division is more complex due to above factors

4. Eukaryotic Cell Cycle

5. Eukaryotic Cell Division Division of nonreproductive cells is called “Mitosis” Nonreproductive cells are referred to as “Somatic Cells” Mitosis involves the even division of chromosomes and organelles between two cells that are not part of the reproductive system The parent cell undergoing Mitosis has a Diploid number (2n) of chromosomes The two daughter cells that result from Mitosis have a Diploid number(2n) of chromosomes

6. Eukaryotic Cell Division Division of reproductive cells is called “Meiosis” Reproductive cells are referred to as “Germ Cells”, and upon completion of Meiosis those cells are called “Gametes” Meiosis is often referred to as “Reduction Division” because the number of chromosomes is reduced from the Diploid number (2n) to the Haploid number (n) One parent cell with a Diploid number results in four daughter cells with a Haploid number

7. Chromosomes First observed by German Embryologist Walther Fleming 1882 What he saw under his primitive microscope were thread-like structures of salamander larval cells appearing to separate lengthwise He called the division “Mitosis” based on the Greek word “Mitos”, meaning thread Number of chromosomes vary greatly by species: Humans (46), House Cat (18), Plants (100’s)

8. Chromosomes In Somatic Cells, Chromosomes group together in pairs based on size and genetic information; they are called “Homologous Chromosomes” or “Homologues” Before cell division, each Homologous Chromosome replicates resulting in two identical copies called “Sister Chromatids” The “Sister Chromatids” remain joined after duplication and prior to cell division at the center or their structures; this area is called the “Centromere”

9. Chromatin During Interphase, the macromolecular complex of DNA and Protein is referred to as “Chromatin”, as stated previously Chromatin is 40% DNA and 60% Protein The reason there is a large proportion of protein associated with the DNA structure is chemical in nature The proteins allow the DNA to thicken and coil in preparation for cell division; if there were no proteins present, this would not happen

10. Chromosomes Often in discussion, the long strands of DNA are called “Chromosomes” However, DNA strands are actually referred to as “Chromosomes” only during cell division (whether it is mitosis or meiosis) The above is the case because it is just prior to cell division that the DNA strands thicken and coil taking on a unique appearance, that of a “Chromosome” Throughout the majority of the cell cycle (Interphase), the DNA strands are called “Chromatin”

11. Cell Division • Cell Division takes approximately 1 hour of the 24 hour Cell Cycle • Cell Division has four distinct phases • Some scientists further subdivide those phases into five or more • The four phases in order are: • A) Prophase • B) Metaphase • C) Anaphase • D) Telophase

12. Prophase 1. Chromosomes begin to migrate to the center of the cell 2. Chromosomes also pair up with their homologue 3. The Nuclear membrane degrades 4. The Centrioles appear, migrate to opposite ends of the cell, and project their Spindle Fibers outward toward the Centromeres of the Chromosomes

13. Prophase

14. Metaphase 1. The Chromosomes are lined up in the middle of the cell 2. The Nuclear Membrane has completely disintegrated 3. The Centrioles’ Spindle Fibers attach to the centers of the Chromosomes, the Centromeres, in preparation to pull the Chromosomes apart

15. Metaphase

16. Anaphase 1. Spindle Fibers from the Centrioles pull the Chromosomes apart toward opposite ends of the cell 2. Once the Chromosomes separate they are referred to as “Sister Chromatids”

17. Anaphase

18. Telophase 1. Each set of Sister Chromatids has been pulled to opposite ends of the parent cell 2. The Nuclear Membrane begins to reform around two new nuclei (the locations of the sister chromatids) 3. The Sister Chromatids begin to uncoil and loosen, and now are designated as Chromosomes 4. The Plasma Membrane of the parent cell begins to “pinch off” into two new membranes via “Cytokinesis” 5. The Centrioles deactivate and “disappear” into the cytoplasm

19. Telophase

20. Miscellaneous Cell Cycle Information Cytokinesis – the division of the cytoplasm at the end of cellular division Cleavage Furrow – the physical action of the parent cell’s cytoplasm being pinched apart during Cytokinesis Mitosis is sometimes referred to as “Karyokinesis” Plant cells use a “Cell Plate” (wall in the center of the parent cell) to divide the cytoplasm instead of a “Cleavage Furrow” It is important to understand that a cell does not necessarily divide every 24 hours: it can enter a “stasis” until environmental conditions are more favorable

21. Cancer Old/malfunctioning cells do not die and continue to reproduce improperly functioning cells Bundles of cells that are malformed are called “Tumors” Some of the cells in the tumor can then migrate to other parts of the body, thereby enabling the proliferation of more cancerous cells/tumors in other locations: “Metastases”

22. Cancer Treatment The conventional approach to treating, and hopefully curing cancer, is Chemotherapy and Radiation Chemotherapy – a chemical that is delivered to the person usually intravenously; the drug targets and kills cancer cells Radiation – high frequency energy delivered to a person’s body via a machine in an effort to target and kill cancer cells There are many forms of cancer each with a unique set of treatment options