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Cell Division and Mitosis

Cell Division and Mitosis. Ch. 5. God’s Command to Nature. Genesis God created all living things and gave them a command: “Be fruitful and multiply, fill the earth and subdue it…”. Cell Division . There are FOUR main functions of Cell Division:

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Cell Division and Mitosis

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  1. Cell Division and Mitosis Ch. 5

  2. God’s Command to Nature Genesis God created all living things and gave them a command: “Be fruitful and multiply, fill the earth and subdue it…”

  3. Cell Division There are FOUR main functions of Cell Division: • 1. In unicellular organisms, cell division is the way these organisms reproduce. • The cell DIVIDES producing a duplicate or copy of itself

  4. Cell Division • In multicellular organisms, cell division has several functions: • 2. Regeneration- occurs when parts or organisms that have been damaged grow back or are replaced. • Ex. A starfish can grow a new arm if one is cut off. • Do you know of any other animals that can replace lost parts?

  5. Cell Division • 3. Healing- another function of cell division is the healing of wounds. • Whenever you have a cut or scrape on your skin, you can see the healing take place over a period of time. • While the wound heals, new cells are made through cell division to replace the destroyed and damaged cells.

  6. Cell Division • 4. A fourth important result of cell division is the growing process. • After a cell divides, both new cells grow and divide to form more new cells • Some cells can divide every few hours

  7. Prokaryotic Cell Division • Bacterial cells reproduce by Binary Fission • Begins with DNA replication; each copy moves to opposite sides of cell • Followed by elongation of cell, and formation of a septum (separation) between the two halves, forming two new cells • Results in two cells that are identical (clones) of original cells

  8. Binary Fission

  9. Eukaryotic Cell Division Two forms • Mitosis • grow, replace dead or worn out cells, or to repair wounds • Asexual reproduction in fungi, protists, some plants/animals • Meiosis • Formation of gametes for sexual reproduction

  10. The Cell Cycle • The length of time the cell cycle takes depends on the type of cell. • Usually the more specialized the cell the less likely it is to divide.

  11. Ever wondered how often your cells regenerate? Intestinal lining 2 to 30 days Skin 21 to 30 days Red blood cells 90 to 120 days The pancreas 5 to 12 months Muscles 6 months to 3 years Tissues 1 to 7 years Bones 8 months to 4 years

  12. Cell Cycle interphase G1 S telophase anaphase Mitosis G2 metaphase prophase

  13. The Cell Cycle: Interphase When a cell is not dividing it is said to be in Interphase: • G1: Gap 1, cells are recovering from an earlier cell division, synthesizing organelles and growing  • S: Synthesis, DNA replication occurs • G2: Gap, cells are making sure all the DNA was replicated correctly; a little more growth; the chromosomes start to undergo condensation, becoming tightly coiled; Centrioles (microtubule-organizing centers) replicate and one centriole moves to each pole.

  14. Interphase interphase

  15. DNA and Cell Division (Interphase) • During cell division, the genetic material DNA, needs to be copied and divided between the two new cells • DNA in cells is divided into long chains called chromosomes(“volumes” of DNA) • Chromosome DNA is wrapped around proteins called histonesto organize it

  16. Eukaryotic Chromosome Structure • Normally, chromosomes are spread out in a form called chromatin • During mitosis, chromatin folds up and condense to become chromosomes

  17. Eukaryotic Chromosomes • Chromosomes must be replicated before cell division. • sister chromatids: are 2 copies of the chromosome • The sister chromatids are bound together in the middle at a centromere

  18. chromosome (unduplicated) in cell at interphase same chromosome (duplicated) in interphase prior to mitosis mitosis, cytoplasmic division chromosome (unduplicated) in daughter cell at interphase chromosome (unduplicated) in daughter cell at interphase Maintaining Chromosome Number

  19. The Cell Cycle: Cell Division • Mitosis (M Phase) • Nuclear Division • Cytokinesis (C phase) • Cytoplasmic Division

  20. The Cell Cycle G0

  21. Mitosis • Nuclear Division • Dividing up the genetic material (DNA)

  22. Mitosis Mitosis is divided into 4 phases: 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase

  23. Mitosis • 1. Prophase: • chromosomes condense and appear as sister chromatids joined at centromere • cytoskeleton disassembles • centrioles move to each pole of the cell; spindle apparatus is assembled • nuclear envelope dissolves

  24. The Spindle Apparatus • Consists of two distinct sets of microtubules • Each set extends from one of the cell poles • Two sets overlap at spindle equator • Moves chromosomes during mitosis • In both plant and animal cells, spindle fibers originate from centrosomes; in animal cells, centrosomes are called centrioles

  25. Spindle Apparatus one spindle pole one of the condensed chromosomes spindle equator microtubules organized as a spindle apparatus one spindle pole

  26. Prophase

  27. Mitosis 2. Metaphase: -spindle fibers pull the chromosomes to align them at the center of the cell (in the “middle” of the cell) called the metaphase plate

  28. Metaphase

  29. Mitosis 3. Anaphase: - microtubules pull sister chromatids away toward the poles

  30. Anaphase

  31. Mitosis 4. Telophase: -spindle apparatus disassembles -nuclear envelope forms around each set of sister chromatids -chromosomes begin to uncoil -nucleolus reappears in each new nucleus

  32. Telophase

  33. Cytokinesis • Division of the cytoplasm • Usually occurs between late anaphase and end of telophase • Two mechanisms • Cell plate formation (plants) • Cleavage furrow (animals)

  34. Cytokinesis: Animal Cell • Cleavage furrow – is the pinching in of the cell membrane to divide the cell into 2 new cells

  35. Cleavage Furrow

  36. Cytokinesis: Plant Cells • Cell Plate Formation • In plant cells, a cell plate will form between the two dividing nuclei to form the new cell wall

  37. Mitosis/Cytokinesis outcome • 1 parent cell  2 identical daughter cells • Chromosome number remains the same from one generation to the next

  38. Mitosis: plant vs. animal cells

  39. Control of the Cell Cycle The cell cycle is controlled at three checkpoints: 1. G1/S checkpoint -the cell “decides” to divide 2. G2/M checkpoint -the cell makes a commitment to mitosis 3. late metaphase (spindle) checkpoint -the cell ensures that all chromosomes are attached to the spindle

  40. Control of the Cell Cycle cyclins – proteins produced in synchrony with the cell cycle -regulate passage of the cell through cell cycle checkpoints cyclin-dependent kinases (Cdks) – enzymes that drive the cell cycle -activated only when bound by a cyclin

  41. Control of the Cell Cycle Proto-oncogenes: -some encode receptors for growth factors -some encode signal transduction proteins -become oncogenes when mutated -oncogenes can cause cancer when they are introduced into a cell

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