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CELL THEORY

CELL THEORY. Cells are the basic unit of life. All living things are made up of one or more cells. All cells come from pre-existing cells. Asexual Reproduction. Asexual Reproduction: Produces offspring identical to the parent.

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CELL THEORY

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  1. CELL THEORY • Cells are the basic unit of life. • All living things are made up of one or more cells. • All cells come from pre-existing cells.

  2. Asexual Reproduction • Asexual Reproduction: Produces offspring identical to the parent. • EX. Budding: a type of asexual reproduction in which a cell or group of cells pinch off from the parent to form a new individual. • EX. Mitosis (Oh My toes): want the same kind of cells on your toes. • Mitosis is a type of asexual reproduction when a nucleus undergoes cell division in which two daughter cells are formed, each containing a complete set of chromosomes.

  3. Cell Division • Two Types • Meiosis (Sexual Reproduction) • Sex Cells (Sperm or Egg) • Mitosis (Asexual Reproduction) • 2 Daughter cells (similar cells)

  4. Cell Cycle/Cell Division Cell Cycle is the pattern of division & growth of a cell. It involves the copy & distribution of the genome (genetic information/DNA).

  5. The cell cycle serves 3 main functions…. • Reproduction • In single-celled organisms, 2 separate individual organisms are the result of the cell cycle. • Growth & development • In multi-cellular organisms, rapid copying of cells via the cell cycle add to the growing organism. • Tissue & renewal • In multi-cellular organisms that have reached maximum growth, the cell cycle renews & replaces older cells to maintain and organism’s size & function.

  6. Cell Division/Cell Cycle • Mitosis: • Mitosis (Oh My toes): want the same kind of cells on your toes. • Mitosis is a type of asexual reproduction when a nucleus undergoes cell division in which two daughter cells are formed, each containing a complete set of chromosomes.

  7. Continue Cell Cycle • Somatic cells are all the body’s cells except the reproductive cells; egg & sperm. • Somatic cells contain 46 chromosomes. • Chromosomes are condensed chromatin into double rods (chromatids) of genetic material. • Chromatin • The mass of very long, thin fibers of DNA & proteins that are found unwound within the nucleus. • Chromatid • ½ of the double-rodded structure of a chromosome

  8. 3 Stages of Cell Division/Cell Cycle • Interphase(Cell is getting ready) • Mitosis (Cell Division-4 phases) • Cytokinesis(Chop/2 cells)

  9. Interphase • Stage 1: Interphase (21 hours) • Interphase is the longest of the 3 stages of the Cell Cycle • The cell begins to grow & enlarge • Replication of DNA

  10. The primary process that takes place during Interphase is the replication of DNA. • DNA (deoxyribonucleic acid) is the sequence of nitrogen base pairs that determines the structure of proteins and serves as the genetic code of life. • Replication is the process by which the DNA makes an exact copy of itself.

  11. The cell produces structures that will be used to help the cell divide into 2 new cells. • Centromere connects the chromatids or double rods of chromosomes. • Centrioles are organelles used to separate & pull chromosomes into new nuclei. • Spindle fibers are bands that extend from the centriole & attach to the chromosome & pull it into separate nuclei.

  12. Interphase

  13. Stage 2: Mitosis • Mitosis • 4 Phases • Mitosis is the 2nd stage of the Cell Cycle and takes <50 minutes. • During Mitosis, 2 nuclei are created and 1 copy of the DNA created during Interphase is distributed to each of the nuclei. • (Falwell) My toes…You want the same cells for skin cells, toe nails, hair etc. • Remember: Skin cells, hair cells, etc, are Somatic Cells

  14. 4 Phases of Mitosis • Prophase • Metaphase • Anaphase • Telophase

  15. Prophase (1st phase of Mitosis) • Prophase is the longest phase of Mitosis. • Chromatin in the nucleus condenses to form chromosomes. • Spindle fibers form a bridge between the ends of the cell. • Nuclear envelope breaks down

  16. Prophase

  17. Prometaphase • Recently a new phase; Prometaphase, has been added in between Prophaseand Metaphase. • Centrioles move to opposite sides of the nucleus. • Kinetochore is a specialized structure located at the centromere region forms.

  18. Metaphase • Chromosomes line up across the metaphase plate, an imaginary plane located across the center of the cell. • Each chromosome attaches to a spindle fiber at its centromere

  19. Metaphase

  20. Anaphase • The centromere split. • The 2 chromatids separate. • 1 chromatid is drawn by its spindle fiber to 1 end of the cell. • The other chromatid moves to the opposite end. • Cell stretches out as the opposite ends are pushed apart.

  21. Anaphase

  22. Telophase • Chromosomes begin to stretch out & lose their rod like appearance. • A new nuclear envelope forms around each region of chromosomes.

  23. Telophase

  24. The End of Mitosis

  25. Remember 3 stages of cell division/cell cycle • Stage 1: Interphase • Stage 2: Mitosis • Phase 1: Prophase • Phase 2: Metaphase • Phase 3: Anaphase • Phase 4: Telophase • Stage 3: Cytokinesis

  26. Stage 3: Cytokinesis • Cytokinesis (< 15 minutes) • The cytoplasm divides. • The 1st sign of cleavage is the appearance of a cleavage furrow. • A cleavage furrow is shallow groove in the cell surface near the old metaphase plate. • Cytokinesis actually begins during Telophase, the last phase of Mitosis. • 2 new cell membranes form around the 2 new cells. • The new cells have an identical set of chromosomes and half of the organelles

  27. Cytokinesis

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