competencies 1 characterize the phases n.
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  1. Competencies 1. characterize the phases of the cell cycle and their control points - STEM_BIO11/12-Id-f-6 2. describe the stages of mitosis/meiosis given 2n=6- STEM_BIO11/12-Id-f-7 3. explain the significance or applications of mitosis/meiosis- STEM_BIO11/12-Id-f-9


  3. Short Video ClipGuide Questions:1. What is mitosis?2. What are the stages of Mitosis?3. What happens in every stage of mitosis?4. What is the importance of mitosis?

  4. 10X Magnification of Stained Human Cheek Cells

  5. Parts of the Human Cheek Cell at 40X Magnification

  6. Can you name these parts of the Human Cheek Cell?

  7. Centrioles : Nuclear division

  8. CELL DIVISION – Mitosis Cell Life Cycle – series of changes a cell goes through from time it is formed until it divides. Two Events: 1. Cytokinesis – division of cytoplasm 2. Karyokinesis – division of nucleus

  9. The original cell is called the parent cell; 2 new cells are called daughter cells • Before cell division occurs , the cell replicates (copies) all of its DNA, so each daughter cell gets complete set of genetic information from parent cell • Each daughter cell is exactly like the parent cell – same kind and number of chromosomes as the original cell 2 Daughter Cells Parent Cell

  10. Many organisms, especially unicellular organisms, reproduce by means of cell division – called asexual reproduction – Ex: bacteria

  11. DNA • DNA is located in the nucleus and controls all cell activities including cell division • Long and thread-like DNA in a non-dividing cell is called chromatin • Doubled, coiled, short DNA in a dividing cell is called chromosome • Consists of 2 parts: chromatidand centromere

  12. Chromosome number • Every organism has its own specific number of chromosomes • Examples: Human = 46 chromosomes or 23 pairs • Dog = 78 chromosomes or 39 pairs • Goldfish = 94 chromosomes or 47 pairs • Lettuce = 18 chromosomes or 9 pairs

  13. All somatic (body) cells in an organism have the same kind and number of chromosomes • Examples: Human = 46 chromosomes • Human skin cell = 46 chromosomes • Human heart cell = 46 chromosomes • Human muscle cell = 46 chromosomes • Fruit fly = 8 chromosomes • Fruit fly skin cell = 8 chromosomes • Fruit fly heart cell = 8 chromosomes • Fruit fly muscle cell = 8 chromosomes

  14. Cell Cycle -- series of events cells go through as they grow and divide • Cell grows, prepares for division, then divides to form 2 daughter cells – each of which then begins the cycle again


  16. Stages: • Interphase • – resting stage • – preparatory stage. • - Accumulation of materials.

  17. During Interphase DNA replicates which must occur before Mitosis can begin .

  18. Interphase—period of cell growth and development • DNA replication (copying) occurs during Interphase • During Interphase the cell also grows, carries out normal cell activities, replicates all other organelles • The cell spends most of its life cycle in Interphase


  20. Interphase This cell is shown, as this is how all cells look before mitosis. Please be aware that Interphase is a phase of the cell cycle, but NOT a stage of mitosis.

  21. Prophase • – Chromatin threads coil and shorten and visible bar-like bodies called chromosomes appear. • - each chromosomes is made up of two strand – Chromatid held by a button-like – Centromere. • - centriole separate and move to poles directing to the assembly of mitotic spindle. • - by end of prophase nuclear membrane and nucleoli broke down and disappearance attached to spindle fiber by centromere.

  22. Mitosis - Early Prophase To begin mitosis, the nuclear membrane breaks down, while the chromosomes shorten and thicken (here, a chromosome is two chromatids, bound at a point called the centromere, making an "X" shape). The other structures important for mitosis are also forming (i.e. the centrioles).

  23. Prophase • Chromosomes coil up • Nuclear envelope disappears • Spindle fibersform

  24. 3. Metaphase – • short stage • – chromosomes aligned at the center of the spindle are attached into it.

  25. Mitosis - Metaphase The spindle has now formed and the nuclear membrane has broken down. The chromosomes are lined up along the cell's center and are attached to the spindle fibers. When the individual chromatids (½ of the "X") are separated from the chromosome (the "X"), they are now each referred to as a chromosome

  26. Metaphase—(Middle) • Chromosomes line up in middle of cell • Spindle fibers connect to chromosomes

  27. Anaphase • – centromere split and chromatids move slowly apart towards the end of poles.

  28. Mitosis - Anaphase The newly formed chromosomes are pulled along the spindle toward opposite poles of the cell.

  29. The X is pointing to what structure?

  30. Anaphase—(Apart) • Chromosome copies divide • Spindle fibers pull chromosomes to opposite poles

  31. 5. Telophase – prophase in reverse. - chromosomes at poles uncoil to become thread like chromatin again. - Spindle break down and disappear. - Nuclear membrane forms around each chromatin mass and nucleoli appear in each daughter nuclei.

  32. Mitosis - Telophase The chromosomes have finished their migration to the poles. The spindle has broken down and disappeared. The cell membrane pinches in (forms a cleavage furrow) along the center creating two separate cells . At this time, the chromosomes uncoil and become less visible (as they are during Interphase), the nuclear membrane reforms. The division of the cytoplasm is called cytokinesis. The division of the nucleus is Mitosis. At the end of Telophase, the cell reenters Interphase.

  33. Telophase—(Two) • Chromosomes uncoil • Nuclear envelopes form • 2 new nuclei are formed • Spindle fibers disappear

  34. View of onion root tip under low power

  35. MITOSIS – ONION ROOT TIP Interphase Prophase Later Prophase Metaphase Telophase Early Anaphase Later Telophase Anaphase

  36. Summary: Cell Cycle • Interphase Mitosis (PMAT) Cytokinesis • When cells become old or damaged, they die and are replaced with new cells

  37. What is the importance of Mitosis? Importance of Mitosis: 1. Qualitative - daughter cells are exactly the same with the mother cells. 2. Quantitative - equal distribution of hereditary units.

  38. Why do cells need to divide? • Living things grow by producing more cells, NOT because each cell increases in size • Repair of damaged tissue • If cell gets too big, it cannot get enough nutrients into the cell and wastes out of the cell

  39. Cell Division Control • DNA controls all cell activities including cell division • Some cells lose their ability to control their rate of cell division – the DNA of these cells has become damaged or changed (mutated) • These super-dividing cells form masses called tumors

  40. Benign tumors are not cancerous – these cells do not spread to other parts of the body • Malignant tumors are cancerous – these cells break loose and can invade and destroy healthy tissue in other parts of the body (called metastasis)

  41. Cancer is not just one disease, but many diseases – over 100different types of cancers