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Mitosis and the Cell Cycle

Mitosis and the Cell Cycle. Chromosomes. Made of tightly coiled DNA and proteins Chromatid = 2 identical halves of a chromosome. Called “sister chromatids” Centromere= point where chromatids join Chromatin = uncoiled chromosome during Interphase DNA= thin strands of chromatin.

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Mitosis and the Cell Cycle

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  1. Mitosis and the Cell Cycle

  2. Chromosomes • Made of tightly coiled DNA and proteins • Chromatid= 2 identical halves of a chromosome. • Called “sister chromatids” • Centromere= point where chromatids join • Chromatin= uncoiled chromosome • during Interphase DNA= thin strands of chromatin. • DNA is easier to use/transcribe when uncoiled • DNA is easier to move around when tightly packed into chromosomes for cell division. Shown after replication in S phase In G1, chromosomes are haploid (1 half)

  3. Cell Cycle • The dividing and non-dividing (growth) stages in the life of the cell. • Phases: • Interphase (growth & DNA replication) • Mitosis (4 stages of nuclear division) • Cytokinesis (separation of the cytoplasm) • http://www.cellsalive.com/cell_cycle.htm

  4. INTERPHASE90% of cell’s life: • G1: “Growth 1” (or Gap 1) • Growth, cell metabolism and function • S: “Synthesis” • DNA replication • G2: “Growth 2” (or Gap 2) • Extra growth and preparation for division (M phase) *cell also has other organelles

  5. CELL DIVISION • Cells need to divide when: • A cell gets too big to support itself • New cells are needed for repair or replacement • An organism’s body grows • Mitosis is asexual- no new genes mixed in • Bacteria & other single celled organisms do binary fission for reproduction • Another form of asexual reproduction • No genetic variation, unless mutation occurs.

  6. Phases of MITOSIS • Prophase • Metaphase • Anaphase • Telophase • PMAT!

  7. PROPHASE • Longest part of mitosis • The chromatin coils into chromosomes • So they’re packed, easier to move around. • The CENTRIOLES move to the poles • Only in ANIMAL cells (no centrioles in plants) • The spindle forms, attaches to chromosomes • The nuclear membrane & nucleolus break down. • Allows chromosomes to escape centrioles =Organelles that are always in animal cells, mostly used in mitosis

  8. METAPHASE • “Meta”= middle • Chromosomes line up at the middle, pulled like a tug-o-war from the spindles at each pole of the dividing cell

  9. ANAPHASE • Centromeres split • Chromosomes split (from diploid to haploid) • The sister chromatids get torn apart and begin to move toward opposite poles. • Each sister chromatid now becomes a chromosome (With only 1 copy of DNA= haploid)

  10. TELOPHASE • The chromosomes uncoil ( = chromatin) • Nuclear membrane reforms around each new set of chromosomes. • The spindle breaks down • Centrioles leave poles. “cleavage furrow” starts to form in animal cells

  11. CYTOKINESIS • The cytoplasm splits into 2 separate, genetically identical “DAUGHTER CELLS.” • Cell division is complete. • Animal cells = “cleavage” • Cell membrane pinches to form 2 separate cells • Plant cells form a new Cell Wall (= “cell plate”) Plant Animal

  12. CELL CYCLE: BIG PICTURE Cytokinesis

  13. UNCONTROLLED CELL DIVISION(a.k.a. “Cells Gone Wild”) • CANCER = when cells don’t stop dividing • They are unable to receive normal chemical signals from the body that would stop division. • Sometimes inherited (runs in the family) • Sometimes environmental (damaged DNA) • TUMORS are masses of unnecessary cells. • Can be benign (harmless, doesn’t spread) • Can be malignant (invasive, spreads, “metastasizes”)

  14. A B C D E What phases are these onion cells in?

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